Kohaku/Synopsis

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Kohaku was born around 3,700 years after the mysterious petrification incident. After her sister Ruri became ill, she brought Ruri every day hot spring water to buy her time.

Synopsis

Vs. Tsukasa Arc

She is first briefly seen, tending a fire.

Kingdom of Science Arc

She notices another fire and starts to think others are around. She signaled to them for a response.

She witnesses the apparent sacrifice of Senku to Tsukasa in exchange for Yuzuriha's life. She then tails Tsukasa, only to be noticed and inquired who she is. Not answering to her opponent's question, she assaults Tsukasa instead, mentioning how there's no need for introduction since he'll make greetings and apologies in hell for killing the "sorcerer" gentleman.

Tsukasa, having figured out she's not a person from modern times, concludes she is a descendant of someone who was not petrified in the past. He abruptly stops Kohaku's attack with two fingers and decides to rush for the cave of miracles instead, assuring himself he could kill primitive villagers easily if they posed an obstacle. He promptly slashes a tree and traps Kohaku under it.

She is found by Senku who offers her to choices in order to save her - to either risk an explosion if she cannot hold out under the pressure or to make her wait by crafting a tool to pull the tree off of her. Kohaku picks waiting, saying she can hold out. Kohaku is amazed by Senku's invention, and after he pulls the fallen tree she says she has taken quite a liking to him.

Senku being as he is, is appalled by that declaration, berating her for falling in love with him in such an emergency situation. A flustered Kohaku denies the claim and tells Senku she simply meant she likes people like him and wants to work for him. Senku is glad, saying that affection and love are the root of most illogical problems. Later in the day, Senku makes fun of Kohaku sleeping with a knife, with Kohaku warning him that even though she's interested in him, she still doesn't trust him completely. Senku quickly rebukes the threat by saying he would have no chance of attacking a "lionesss" by her even in her sleep, much to Kohaku's embarrassment.

As they begin heading for the village, Kohaku asks Senku if he was fighting Tsukasa, offering him an alliance to stop him. Once they start making their way to their destination, Kohaku stumbles under the baggage of water. Senku offers to carry it, not before asking why a healthy lioness like her would need water. Kohaku, embarrassed again, informs Senku it's for her sick sister. Lamenting over her sister's ailment, she compassionately says she would give her healthy body in order to recover her sister from her sickness. It's not long before Senku gets overwhelmed by the cup's weight. He creates a makeshift trolley in order to quickly reach Kohaku's village, Kohaku being amazed once again by his inventions.

Senku is immediately attacked by the village's gatekeepers, Kinro and Ginro, as Kohaku orders them to cease their assault. Kinro states that rules of the village must be respected, while Ginro states it's his first time meeting a human and that all humans outside the village are likely to be exiled criminals. Kohaku resorts to threatening them with a fight should they refuse. Senku neutralizes the situation shortly after by fascinating the gatekeepers with a flurry of balloons.

She, along with the two brothers witnesses a "sorcery" showoff with Chrome and Senku. As Senku keeps dominating the battle, Chrome eventually challenges him to a battle of arithmetic, promising to relinquish all of his possessions should he lose. Kohaku says this battle will be a breeze for Senku, and true enough, Senku dominates the competition and thereby wins over all of Chrome's collections.

As she brings the water to Ruri, she is questioned by the village guards about the lack of barrels that were intended. In order not to worry the guards and his sister, Kohaku lies about falling asleep while carrying the barrels, only to be scolded by the guards on how she should be taking this task more seriously. Ruri asks them both to leave as she pleads Kohaku not to push herself so much for her sake, noticing the knot on her hair changed and that she must've gotten into some trouble that made it fall off to begin with.

A day later, Kohaku pledges that she will do anything she can to aids Senku in curing Ruri. Senku explains that in order to make a cure in current conditions, they have two possibilities. They can either pick the biological route to penicillin, which is made out of blue mold. However, they'd be relying on a game of probability, which is uncertain to succeed. On the other hand, they could pick the sulfonamides route, which is made from stone. This is the safer course, although it will take immense amount of determination and work.

Senku then goes on to draw a map to making the cure, which shocks both Kohaku and Chrome due to its complexity. Kohaku then says that even if Senku tries to explain anything in the map, she wouldn't understand it. In midst of their discussion, Kohaku and Chrome are shocked again to find out the earth was actually spinning all this time. Kohaku then asks why she isn't being knocked off a tree she's standing on, with Senku replying it's due to gravity. Senku mentions the north star, which is the most useful one for navigation as it always points to north, true to its name. Kohaku mentions that it's slightly off north duo to her inhuman perception, with Senku concluding Earth's axis must have tilted.

Surprised, Senku praises Kohaku and Chrome for being more perceptive than he is, saying that he feels useless. Kohaku comforts him by saying her impression of him is that he is not useless at all. Kohaku is next seen using a magnet that Chrome found in order to acquire iron for Senku.

While going down the river in order to attach residual iron to a magnet, Senku and Chrome discuss Kohaku's strength while calling her a gorilla, much to Kohaku's chagrin. Kohaku then angrily complains that they should help her collect iron themselves, while being interrupted by a girl called Suika. Suika tells them she wants to help, as she usually isn't of some use due to wearing her melon helmet all the time. Senku welcomes Suika's help as Suika gets amazed that Senku is the first person who hasn't inquired her about why she's wearing the helmet, perhaps because he realized she doesn't want to show her face and is nice to her. Kohaku quickly responds that Suika shouldn't glorify Senku since she doesn't know him well, with Chrome in pair saying Senku simply doesn't care.

Chrome and Senku discuss the story of "Momotaro" which Senku traces to his own times, as Chrome and Kohaku inform Senku that Ruri tells them many stories like Momotaro which contain numerous words that are hard to understand - greatly piquing Senku's interests since it's a mystery how a villager knows children's fictional story that existed 3,700 years ago. As Chrome gets startled by Senku's exclamation of interest for Ruri, Kohaku warns Senku that Chrome has affections for Ruri. Kohaku comments that since Chrome is so innocent, his affection is at a subconscious level and that it's adorable seeing him behave like this. Kohaku is next seen helping Senku melt the iron sand they collected.

Suika describes what various villagers desire, mentioning the village's three most attractive girls wanting boyfriends. With Senku dismaying over not being able to fulfill that request, Kohaku mentions that Senku is a ladykiller, but not exactly the type they're looking for. Once Senku decides he will make food to bribe the villagers, Kohaku aids him in making a modern specialty called ramen. With ramen done, Kohaku tries eating it and is amazed how such delicious food exists.

When Senku realizes another modern timer has subtly made his way in the village, due to his familiarity with Cola, Kohaku surrounded him with Kinro and Ginro. She asks Senku if he knows the man and while he doesn't know him personally, he recalled his reputation as a mentalist and revealed his name Gen Asagiri. Kohaku saw through Gen's lies of not knowing Tsukasa and he revealed his mission after Senku made him work, to pay off his gift of ramen.

However, Senku's progress at creating iron and plans of making a generator impressed Gen and prompted him an offer to lie about it and allow Senku to fall under his radar once again. Kohaku called him dirty but was prevented from killing him, as Tsukasa might retaliate with an army. Kohaku then uses Kinro's spear as a lightning receiver. As Kinro's spear is completely destroyed, Kohaku apologizes to Kinro and says it was necessary in order to make magnets.

She warns Senku that some "force" is pulling the two magnets apart while Senku says she got the polarities wrong. They switch the side and the magnet pulls Senku right towards the other part - proving that a very powerful one was made. When Magma attacked Gen, in his anger at the "sorcerer" in the village and due to mistaking him for Senku, Kohaku finds Gen after Magma impales him with his spear.

She declares him dead, though Senku has her examine Gen, showing that he survived due to the bags of fake blood hidden under his clothes in preparation of an attack. She is impressed by his deviousness. After Gen flees to Tsukasa, Kohaku worries about him revealing Senku's status. Senku assures her Gen made his decision already when Senku created light through electricity, that being to join them. The former says that superficial men like Gen have their ways of showing their worth, Gen playing an unpredictable trickster. Kohaku states that all men are troublesome characters, no matter the era.

Kohaku gets informed by Suika that Magma was the perpetrator behind the attack on Gen. She concludes that it was Gen's trick that goaded Magma into thinking he's the sorcerer. Senku asks why Magma wants to kill Kohaku, while the latter responds she stopped him during previous village games, thereby preventing him from becoming a village chief. She overheard him wanting to kill Ruri if she doesn't die quickly, and then proceeded beat him in the finals of the games.

Senku worries about Magma winning the games in the future, making their job much more difficult. Kohaku thinks it's an opportunity to take the place of the chief instead, and approaches Kinro and Ginro at the gate, offering them marriage should they win the fight with Magma. An indecisive Ginro blushes and considers Ruri to be physically attractive, Kinro as usual scolding his brother for his behavior. Kinro then states a gatekeeper's answer shouldn't be taken at all, but he understands what's going on and that Senku is not evil. He asks Kohaku what exactly she wants to do, Kohaku replying she wants to save her sister. Kinro agrees with that and they start training in preparation.

While she trains with Kinro and Ginro, she laments on the fact that Chrome cannot participate despite feeling affection for her sister.

Once Kinro and Ginro approach Senku to goad him into making customized spears for them with an excuse that it will help them fight and practice better, Kohaku figures out that they just want their respective spears from Senku and that the coating shining on them has no battle value at all.

The group arrives to hot springs along their way to get the materials needed for Ruri's cure. Kohaku noting that this is the place she goes to regularly to retrieve the water for Ruri. Eventually, the group reaches their goal - that being emerald green spring. Enchanted by its beauty, Ginro approaches the lake's waters as Senku screams for him to get back. Kohaku leaps in time and snatches Ginro away from hydrogen sulfide. Kohaku assures a panicked Ginro that he's fine, the latter observing a bird being dissolved in the acid.

Senku seemingly comes to a stalemate and Kohaku suggests that she quickly snatches the sulfuric acid since she is ready to risk her life for her sister. Senku immediately stops her to tell her about a group that went to investigate a similar sulfuric acid area. The leader of the group knelt down to tie a shoelace, very quickly dying before he even got the chance to tie it up. Senku warns Kohaku that regardless of what speed she possesses, it would be impossible to collect the sulfuric acid. A desperate Kohaku asks Senku what's to be done, as Senku replies they will simply make gas masks to stop the gas from poisoning them.

Having seen Senku's offer to Chrome about obtaining scientific knowledge and protecting him from harm of the emerald springs with Chrome outright rejecting it by saying as friends they should have each other's backs and not be fine with either dying at all, Kohaku compares Chrome to herself. She reminisces about Kokuyo ordering Kohaku to become the next priestess as Ruri's body is soon to give in, which she angrily rejects, saying she is not gonna accept her sister's death. She tells Chrome it's saddening he doesn't have much physical capability to win Ruri over in the tournament and asks Chrome whether he would like her as his wife instead. Chrome tells her that she is a gorilla and nothing like Ruri, prompting Kohaku to pummel him. He then makes fun of Kohaku, teasing her about being in love with him which Kohaku rejects. Chrome scolds her for talking about potential marriage despite not meaning it truly.

Some time later, Kohaku aids the group in making gas masks for the acquisition of sulfuric acid.

Village Games Arc

With sulfuric acid gathered, Kohaku witnesses the making of different chemical compounds in order to eventually synthesize a cure for Ruri, concerned with Senku's descriptions and the substances' behavior. After that's done, Kohaku is shocked that Senku will also participate in the Village Games besides Kinro and Ginro, as the group needs alcohol as a final component in the cure formula. Kinro is appalled by Ginro, Senku and Chrome's alliance to cheat through the village games. He asks Kohaku whether she is fine with this and she confirms, greatly distressing Kinro who wants to win by rules.

Having heard Mantle warn the Kingdom of Science team of Suika's supposed predicament, she warns Senku and Chrome who completely distrust Mantle's claim of Suika drowning in order to gather herbs that there still might be a chance that she's in trouble. She quickly storms off in order to help Suika, with Mantle completing his task of distracting Kohaku from joining the village games.

Kohaku rushes to the village as Magma tells his lackey to surrender in order to disqualify her. Suika fervently apologizes for being captured by Mantle, saying that this is the reason why Kohaku is out of the competition. Kohaku hugs her and says all she cares about is that Suika is fine and that Mantle was lying.

Once it's time to fight Magma, Kohaku solemnly states that neither a battered Ginro nor a physically weak Chrome have any chance of beating him.To everyone's surprise, Chrome succeeds in igniting Magma's clothes with lens from Suika's helmet, making him panic and quickly stunning him with a hit to the groin. With this, Chrome's opponent stumbles and falls into the surrounding water around the island, making Chrome the winner of the match.

The group celebrates Chrome's victory. The celebration, however, is cut short when Ginro misunderstands Ruri and thinks she is indifferent about marrying the winner of the bout, trying to forcefully win it himself and become the chief himself. Kohaku is outraged at Ginro's behavior along with the rest of the village, worrying about how a physically lacking Senku will deal with him. As Senku cunningly defeats Ginro and prepares to surrender the match to Chrome, the latter faints once relieved that the Kingdom of Science has won. An uneasy Kohaku realizes along with the rest of the village that it is Senku who won the village games by accident.

As Senku orders alcohol to be brought to him, Ruri's condition worsens and she vomits blood, greatly startling Kohaku. The villagers are glad alcohol is brought and say that they will drink until the morning in celebration of Senku's marriage. Senku replies with wanting a divorce, much to everyone's shock. As the scientist drags Kaseki with him, Kohaku lifts a few barrels of alcohol and states she will explain everything to Ruri once they finish their business. Having dragged Chrome as well with him, Kohaku compliments Senku on not forcing Chrome to work while being injured. Senku proves her wrong however, and puts ammonia in Chrome's nostrils to abruptly wake him up. She aids in wrapping up the cure by collecting the remaining ingredients. The cure is finally completed, and Kohaku celebrates along with the rest of Kingdom of Science.

When Senku goes on to do an autopsy on a rat to inspect the disease, Kohaku cluelessly inquires whether Senku is going to eat it. Once the autopsy is done, Senku warns that he is unsure which pathogen this is, saying that if it's pulmonary tuberculosis - they would have no chance to cure it, terrifying both Kohaku and Chrome.

Ruri's condition worsens after consuming the cure, prompting Kokuyo to assault Senku who confirms it may be because of the drug. However, the latter concludes this is because the bacteria in question - that being streptococcus pneumonia - is mobilizing its forces as its existence is being threatened, courtesy to the special ability of the pathogen. The former chief goes on to attack Senku again, mistrusting of his intentions. His punch is stopped by Kohaku who states she believes in Senku, along with the rest of the group nodding in unison. With continuous usage, Ruri is ultimately cured of her ailment. Kohaku and her father cry tears of happiness, having finally witnessed their relative being well.

Village Origins Arc

Kohaku is present when Ruri tells Senku about the hundred tales. She is shocked to find out from Senku that Ishigami Village's founder is Senku's father, Byakuya Ishigami.

After getting the gist of the situation, she wonders if everyone in the village is related to Senku and blushes at the possibility. However, she is told that he and Byakuya weren't blood related and the latter was his adoptive father.

Vs. Hyoga Arc

She is worried when Gen tells them of a warrior called Hyoga who is as dangerous as Tsukasa. The thought of such a man standing equal to Tsukasa scared her.

She is shocked to hear Ginro report an attack. Kohaku becomes terrified to watch Hyoga defeat Kinro. She tries to help her wounded friend but is held back by her father since it is dangerous. Fortunately, Senku, with help from Gen creates a ruse that caused the enemy to retreat.

Once the initial fight is over, Kohaku worries about Hyoga and wonders whether Senku has some scientific method to counter his advance. She notices a powerful wind coming down from a mountain, which is a trigger for Tsukasa's army to attack once more. She is then given katanas made by Senku and Kaseki to strike back at the enemy.

Kohaku swiftly dispatches the initial wave of Tsukasa's warriors but is countered once Hyoga arrives to the battlefield with his spearmanship. She is amazed by Hyoga's skill, after he pushes her and the others away. Despite tag teaming with Kinro, she is almost stabbed by Hyoga, but is saved since Gen sabotaged his weapon.

Kohaku is horrified to learn that Hyoga had another ally who set fire to the village. She witnessed the culprit Homura Momiji arrive on the scene. Kohaku orders Ginro to retrieve the children to the science storeroom. After Homura dodged attacks from Kohaku's father, she tries to attack but Homura easily dodged. She later helps Senku in retrieving Suika who lured the enemy away. Providing her friend with a mask, they were able to survive the rest of gas and return to their comrades.

Communications Arc

Once the battle is settled, Senku explains that the enemy's army numbers are alarmingly growing with Gen confirming that the threat is only getting bigger whilst they are missing a critical source for gunpowder. As Kohaku enthusiastically declares agreeing with Senku on a preemptive strike, while Senku claims he will make a most powerful weapon in human history - a cellphone. Kohaku and a fair bit of villagers are shocked to find out such communication advice even exists and the possibility of using it as a weapon in war. Along with the rest of the village, she enjoys a freshly made cotton candy as a part of the testing process for cellphone wire.

Along with Chrome, she worries about Taiju and Yuzuriha's safety, only to be assured by Senku that they will be fine, as they are being held hostage at this point. She gladly offers the shield her father gave her as a memento of the past to be used in the creation of gears to ease the burden of the working for in creation of Senku's inventions, much to Kokuyo's chagrin.

Kohaku has Kinro and Ginro train in preparation for the oncoming battle with Tsukasa. She is amazed to see an ornamented tree made by the crafting club for the first time in her life.

The young warrior complains about the shortage of manpower in response to their resource gathering, and after a wearisome attempt at collecting various stones, is amazed and delighted to see the beauty and usage of a newly acquired material adequate for the oncoming project, tungsten. Along with the rest of the village, Kohaku prepares a grand surprise for Senku's birthday - an observatory. Kohaku marvels at the sight of newfound jewels, playfully making fun of her father's lack of knowledge about their usage. She uses her strength to aid the melting of metals in the process of making the tungsten filament. Kohaku is seen again, participating once more in the finishing touches of making a cellphone's body.

Kohaku inquires about the properties of the cellphone and how the group is gonna communicate to begin with, being shocked that another part needs to be made for it to function like its intended. Nevertheless, the phone can be used if the wires are stretched properly enough, and Chrome and Ruri attempt to converse. Kohaku is excited to see whether Chrome is gonna confess on Ginro's suggestion, only to be let down by Chrome's amazement with science being the subject. She cracks open Byakuya's time capsule for Senku. After the record player is made, she is amazed to hear the village creator's voice through a record while noting he is Senku's father. She notes on how cold Senku is to his father after he disregards a father-son moment. After hearing Byakuya voice his confidence in Senku, she is in awe at the song sung by Lillian.

She notices Homura and is shocked by her knowing everyone in the village. Kohaku defeats her foe after a long chase.

Age of Exploration Arc

Kohaku is amazed to fly in the hot air balloon. She is annoyed at being called a lioness by Senku before she uses her incredible eyesight, she finds the oil fields. She then notes to Senku and Ryusui about the hardships of her Village because of the scarceness of food. She is pleased when Ryusui decides to get farming started but disturbed by his sinister behavior. She remarks on how he is like Gen.

She is later amazed to eat bread after it recreated.

Once it is decided that a chef is needed to be revived, Kohaku is surprised that Ryusui does not even recall the gender of his chef Francois who promptly appears on the scene. Regardless she finds herself enjoying the proper way to cook bread.

She is doing amazed by the new clothes of Kaseki before he destroys them with his usual pose.

She and the others later note on the new signal being located and questioned if this new person is an enemy or ally. She also noted on how Senku, Ryusui, Ukyo, Gen, and Chrome are their wise Generals in this matter. However, she remarks on Chrome. When Senku builds a radar, Kohaku guesses that one part will allow them to see others. She is then surprised to learn that she was right.

Treasure Island Arc

Kohaku and the power team boarded the ship before Ryusui said their names. She then notes on how it was risky leaving their friends alone when Hyoga and Homura were around but is surprised they are prisoners on board.

During the voyage, Kohaku asked Chrome if she had platinum in his collection but he says no. Senku then announces with this substance, they will produce more revival fluid and free more people. She then witnesses a previously unnamed villager, come forward and tells Senku about how his identity never came up. The villager is revealed to be Soyuz, while stating that he was not from Ishigami Village

With Soyuz, the crew realize that there is another human tribe on the island they are heading to. Kohaku was amazed by this after Senku and Ryusui explain that some of the humans came from the island to Japan and are the ancestors of the current residents of Ishigami Village. She soon watches her father question Soyuz after the possibility of Why-man being a member of this tribe is mentioned but she assures her father after he realizes how hard it was for Soyuz. Nevertheless, she tells Soyuz that he is one of them after Senku states wanting to know more is what brought the Kingdom together. Kohaku is then surprised to hear that they will reach land in a few hours and to hear Yuzuriha being used to long lectures. She is then excited when they reach land.

After reaching the island, Kohaku is part of the scouting squad with Senku, Soyuz, and Gen. Once disembarking, the group travel the island until Kohaku reveals that she saw a flash from the direction of the ship.

Kohaku and Senku are alerted by Soyuz and Gen of a strange phenomena before they are shown their petrified allies. Enraged, Kohaku tries to attack the new enemy, but Gen stops Kohaku. After Soyuz notes that seeing the others petrified brought back traumatic memories, they determine the enemy has a device capable of petrifying them. After the group created a microscope, they decide to befriend the female resident of the island to have a way of bringing down the enemy. Following the trail that the woman left they find her being proposed to by other men. Kohaku is confused by the sight.

The group continue to watch the woman revealed to be Amaryllis. They watch as she rejected her suitors while Kohaku states this will be perfect to understand the natives. She is then alarmed when the woman mentions a master. The group briefly wonder how to talk to her until Senku abruptly speaks to her. When Amaryllis takes note of Soyuz, she believed Soyuz to be the island leader because of a supposed resemblance. When the members of her village starts to riot, Kohaku tries to use brute force but Gen stops her because they need allies. As an alternative, the kingdom of science uses teargas to stop them. This display amazes Amaryllis who soon allies with them.

Amaryllis tells the group about her history, as Kohaku was shocked by this news and her plan to infiltrate the harem. Amaryllis is positive about being selected and tries to charm them to help, since their goals align. When the group realize that another woman is needed, Amaryllis questioned where she can find another woman to help. She is given her answer in the form of Kohaku who realizes that she is needed, while the group are surprised. Realizing that the latter's tomboyish nature might be a problem, they decide to give her a makeover

She and the others note on how the enemy have taken the ship. As Kirisame approaches, Kohaku and the latter but she is overwhelmed, due to her dress restraining her movements. Sensing that someone may have survived, Kohaku shouts the word lab, which is something her allies would know in hopes of survival. Gen then plays the situation by making it look Senku and Kohaku were a couple, with Kohaku kissing him to prove it.

Soon her gambit worked, as she sees Ginro survived though disappointed it couldn't have been someone useful, especially begs them for help. However, she settles for it and soon he with help from Suika get the mobile lab. Since the islanders aren't familiar with science, they pass it off as an animal but Kohaku is disgusted when Senku creates fake poop.

Later on, she is given a makeover to ensure she gets selected along with Amaryllis. They also make Ginro disguise himself as a girl before they are sent to infiltrate Ibara's forces.

Before sent off, Senku gives Kohaku earphone earrings, explaining they are a device that could relay messages to her but she is unable to do so with them.

Working together when the girls (along with Ginro) infiltrate the harem, before they are sent items from Senku. Amaryllis covers for Kohaku to possible witnesses, as the pair work together.

After Ibara suspects an invader, he tasks the people with destroying Ryusui's statue. At first, Kohaku is outraged by her ally's statue being damaged and nearly blows her cover. However, to prove that she is not an invader, Senku tells her to destroy the statue. Amaryllis sends the pieces of Ryusui back to the science team.

When Ginro is wounded, she saves him and he tells her what he learned. She realized that she can use this to her advantage and allows herself to get petrified to save Ginro, as the revival formula will heal him. Before being turned to stone she wishes her comrades luck.

She, however, makes the critical mistake of not disposing/destroying her earphone earrings, allowing Ibara to hear Senku's plan.

Once Ibara is defeated, Senku learned where Kohaku and Ginro's statues were. Senku then revived them, with Kohaku punching a grateful Ginro after he tried to grope her. Kohaku then hugged Senku as gratitude for freeing her. Kohaku is on board the ship and keeps the device away from the speaker when Why-man attempts to use it.

New America City Arc

During a sparring match, Kohaku impresses Kirisame with her skill and the latter questions if she was holding back in their fight. Kohaku states she would never be so rude, stating her dress restricted her. Their training scares Ginro who runs off in fear, as the pair chases him. However, he is saved by a newly revived warrior who once served a relative of Ginro. She is annoyed by Ginro taking advantage of the man by making his servants.

The next day, Kohaku helps the others reviving the treasure island villagers. She notices Senku's reaction on the fate of Soyuz' father, knowing Senku could relate. That night, she spots him walking and the pair talk.

After the Perseus returns home, Kohaku helps the others in pressing the weapon to petrify and revive Tsukasa and it’s successful. She soon scolds Chrome who calls her a gorilla.

After Senku and Ryusui reach a disagreement on what course they should take, Gen sides with Ryusui because of the dangerous path Senku has in mind. To settle this, they recreate poker and Gen is on Ryusui's side but Senku accuses him of going to cheat, but Kohaku enters the game. Ultimately, Senku wins the game and his course is chosen.

Kohaku is aboard the ship and pleased when the crew have fun in the bar.

Kohaku watches Senku revive Hyoga for him to help in warrior training. After he agrees but on the condition that he revive two people, she smiles at knowing who. Soon she and revived warriors train on the ship.

Kohaku is present when Senku and Ryusui describe traveling the seas in ancient days. When Senku explains that they can navigate with help from those in Japan, she and the others start to tease Chrome on talking with Ruri. When a storm hits, Chrome has Kohaku create a sunstone prism to better travel. She obliges, after punishing him for calling her a gorilla but is amazed that it can actually help them. Very soon, she is excited when land is spotted.

When they reach San Francisco, the crew of the Perseus separates with the warrior team following the exploration team in the case of an attack. While passing through the river, the Mobile lab is attacked by alligators however, Kohaku and the other Warriors were eager for a challenge and driven by their hunger they attacked most of the beasts while the rest flee in fear. Afterwards, François makes burgers out of the dead alligators to feed the crew, something she is happy on. She is especially by discovering corn and Senku's plan.

They continue to find corn that has been scattered through the river, with Kohaku remarking on how easy the find is. That night, the crew set camp before Tsukasa and the others note on an eerie feeling. Kohaku questions what it is but given no answer. Soon Tsukasa alerts everyone to retreat inside the boat, where they could take cover. Surely enough, bullets rain down and Kohaku joins everyone in ducking for cover. After the gun stops shooting, Ryusui has the group enter the boats before fleeing the scene.

After the Kingdom escape on the river, Kohaku is confused when Ukyo states the enemy is following and states she has been on watch for a while. She is stunned to see an aircraft and tells panicking Gen the unfamiliar person is definitely an enemy, since surely wants them dead before watching Senku have Kirisame bring it down. She is not surprised when Senku and Ryusui decide to procure the plane, as Senku had the look on his face.

Kohaku examines the plane, finding corn on the tires, as the others chalk it up as part of the landing strip. When Senku announced plans to track the enemy, Kohaku is selected along with Gen and Chrome, to pursue the enemy. She is excited at exploring foreign lands. After Gen realized the enemy is drawing them in and feels insulted at being underestimated. Kohaku watches the now driven mentalist tell her and Chrome to stand back while he goes off but not before leaving a trail behind.

Following Gen's trail, the pair discovered the American Fortress, Kohaku was amazed by the sights before wondering about Gen. After Chrome worried about Gen, Kohaku told him that he'll be find. The two then contacted the Perseus to update them on the situation but Tsukasa told them to keep it brief. Soon Senku hung up, to their shock.

While surveying the fortress, they note radio waves could be tracked.

As the two continue going over plans, they are joined by Tsukasa and his group consisting of Suika, Ukyo, and Hyoga. They are relieved because of the extra help. However, they soon get a message from the Perseus in our shocked when it is revealed that Senku was shot.

They soon receive a message from the Perseus and are shocked to hear that one of the members of the American colony Luna has started a relationship with Senku. Kohaku is not too surprised, knowing Senku is (correctly) using them.

South America Arc

After taking a rest on a small island, Kohaku is annoyed by Chrome being excited to travel, despite the enemy pursuing.

While sailing, she wonders if Chrome is eavesdropping on Senku and Xeno but finds him blowing bubbles with them. Unable to understand, she awkwardly leaves.

During the voyage, they make a stop on an island to gather wood for fuel until Taiju (whose unlimited stamina allow him to go on) volunteers to do so alone and Kohaku remarks on this. Later that night, she is surprised when Taiju discovers lights in the sky spelling H-E-L-L and updates them on the situation. The morning after, Chrome and the others find a hanging pumpkin hut belonging to an unknown woman. After seeing her scary squinting expression, they realized that she needed glasses. They learn she is a scientist acquainted with Xeno. Kohaku is exasperated she went the wrong direction because of her poor eyesight but pleased when she says they could go across the continent via motorcycles, prompting Senku to create a roadmap in the steps needed to make one.

When Chrome calls Chelsea a rival after she offers to be their guide, Kohaku remarks it was not a competition. She is then worried when Ukyo announces the enemy is catching up and they don't have much time. After recapping radar with Senku, she brings up how they could use sails to move faster. This cause the group get an idea to use Chelsea's kites as sails to move faster.

After leaping past the mountains, Kohaku reminded everyone of how it made dangerous to leave Hyoga with Xeno.

After Chelsea badgered Luna about her status with Senku, Kohaku made comments because of Senku's nature before remarking she was right after Chelsea stated it wasn't a real relationship.

After Suika found a Petrification Weapon in the river and Chrome called it lucky, Kohaku stated luck had nothing to do with it before she pointed out a large pyramid of weapons.

Kohaku commented on how the pyramid was both beautiful yet disgusting because of its role petrifying Earth. She joins the others in testing the devices in the river but each are duds and disassemble and place them on their stealth ship.

While observing the enemy, Kohaku soon witnesses Maya Biggs suddenly halt, questioning on why. When Maya says that her "instincts as the all-American women's-division MMA champ" are telling her something. After this, she is surprised when Maya immediately spots where she, Tsukasa Shishio and Hyoga were hiding. Realizing they were seen, the group decide to engage them in battle.

Both sides begin a small brawl, and at the start of the fight the Kingdom of Science seems to have the upper hand. During the battle, Kohaku is nearly crushed by Maya with a tree but is saved when Tsukasa impedes Maya. Grateful, Kohaku thanks him before the soldiers that were accompanying Maya to the battle realize he is the MMA champion from Japan. This fact absolutely delights Maya, who begins to target him and goes all out. However, Tsukasa easily bests him by knocking her down in a single blow. After this, one the soldiers uses Maya's defeat to take out Tsukasa with a gun. Distraught, Kohaku calls out to him before she is nearly shot but Hyoga takes the bullet and reminds her to stay focus on her goal. At this, Kohaku accomplished the mission of destroying the communicator before she was dispatched by Stanley Snyder. Stanley inquires to the wounded girl if her goal was to destroy the communicator and she confirms it, earning praise from him. Kohaku was left to die from her wounds, as she and Tsukasa laid wounded in the jungle.

Laying dying, she was not fearful at her impending fate, knowing her allies would defeat Stanley.

Kohaku would be petrified alongside the rest of his comrades as the petrification beam that was launched from America reaches South America.

New Stone World Arc

Three years later, Kohaku's statue is collected by Suika who was revived earlier. Suika takes the time to hug her petrified friend before creating a cart and placing her with her collected allies.

Four years pass, with Suika being able to complete the formula and revive Senku who creates more bottles of fluid. Suika then revives Kohaku, who is shocked to see the older Suika who states that she and Kohaku are about the same age, so she probably can't ask for a hug. However, Kohaku proves her wrong and they share a tearful embrace. Kohaku then watches the revival of everyone else and is pleased by the crew being reunited. She later joins everyone at the celebration.

While preparing new ship, Kohaku soon finds herself confused after Xeno creates the air conditioner and he gives a long explanation. Several days pass with a factory being created, she is soon worried after Xeno states chrome was needed to be dumped in ore to make Superalloy, with her being happy about the aluminum cans that will be used to preserve food, allowing the group to feed cities worth of people in their travel. After countless days, she was greatly happy when Superalloy City was established and several people were revived to inhabit.

When Chelsea brought up the fuel for the new Perseus, Kohaku was excited when Senku said it would run on future energy but she and Suika are dismayed that he used biofuel, which is poop again. After half a year, the ship is functional, it was decided that the group would have to split into three teams if they want to succeed in reviving the whole world. Kohaku is placed with the group that travel the world while collecting materials: Senku, Chrome, Suika, Ryusui, Francois, Chelsea, Kaseki, and Gen. After setting off, Kohaku was amazed by the speed of the new ship and how she never imagined going so fast.