Taiju's parents died when he was young.
A young Taiju would befriend Senku Ishigami and Yuzuriha, where their friendship became unparalleled as they assisted with Senku's experiments. One of their experiments involved deploying light objects into orbit with a self-made rocket. The handicrafts club member, Yuzuriha, made knitted stuffed toys of herself, Senku, and Taiju. The rocket did not make it all the ways to outer space, but it shot the stuffed toys out into space.
Taiju once aided Senku in making a suit for his father Byakuya Ishigami to pass his swimming exam and go into space.
Since high school, Taiju has never hit anyone and he excels in stamina and endurance.
One day, Taiju loudly claims he will profess his 5 years long love for Yuzuriha to Senku. Senku then sarcastically claims he will support him from the school chemistry room, to which Taiju responds with enthusiasm and gratitude.
Senku cuts him off by saying he has no intention of doing so, and berates him from hiding his feelings for over 5 years. Instead of cheering him on, Senku offers him a personally concocted "love potion" which will supposedly guarantee the chance of his feelings reciprocated. Nonetheless, Taiju refuses the offer and tells Senku he will confess to Yuzuriha fairly.
After Taiju leaves, Senku is asked whether the love potion was the real thing with Senku replying it was gasoline and being sure Taiju would certainly refuse the offer given how honest and fair he is.
Taiju invites Yuzuriha to the school yard while being observed by the student crowd, most of them betting on Taiju being rejected with only Senku betting the largest bid on him getting his feelings reciprocated, much to everyone's surprise.
Right before finally confessing, Taiju notices a wide light source appearing from behind them. He decides to shield Yuzuriha from the oncoming light rays, being petrified along with the rest of the world.
While in his petrified state, Taiju exclaims that he's not dead and states that he must keep his concentration in tact or else he will likely fall unconscious. He notices his body is static, like that of a statue and recalls the incident prior to his confession with the bird being petrified and wonders whether the two events are connected, while also reminiscing about him and Yuzuriha bringing two petrified birds for treatment.
At an unknown point in future Taiju wonders how many years it's been since the petrification event. He worries about Yuzuriha but assures himself that a girl like her can't die, and says he will survive as well purely on his willpower. Once again, the time has passed and Taiju has lost track of it, pondering over how long he's been petrified and still unyielding to the petrification and maintaining his consciousness, until he is eventually depetrified.
He observes his surrounding environment, lamenting on the fact that everyone around him got petrified and is still stuck in that state. He eventually decides to revisit the campor tree in order to find Yuzuriha, finding a statue of Tsukasa Shishio along the way. He reaches the tree and thanks it for protecting Yuzuriha from her statue being damaged, promising Yuzuriha he will save her. While talking with the statue, he notices a scribbling on a tree indicating Senku has been depetrified to and is waiting for him down the river. Happily surprised, he meets with Senkuu and tries to hug him while the latter pushes him away, criticizing him for staying "asleep" for so long while he has worked for nearly half a year alone, stating that the day was 5th October 5738. Baffled, Taiju inquires how Senku knew the date and is astounded by the fact that Senku counted in seconds the entire time he was petrified.
They make a plan relying on Senku's brains and Taiju's brawn, aspiring to free the world of the petrification curse and save Yuzuriha.
Taiju is tasked with collecting food while Senku excludes the poisonous herbs and mushrooms. While looking for more food, Taiju finds a cave along the way, with a sculpted bucket collecting a liquid dripping from the cave ceiling. He wonders who put the bucket there only to be refuted by Senku saying it was him.
Senku elaborates that the liquid is nitric acid, a component which could be used to erode stone of petrified statues, however Senku also states that they would need alcohol in order to combine it with nitric acid and form nital to experiment the depetrification process on the statues. Taiju then suggest they can make alcohol out of grapes, an idea that Senku gleefully praises. After 3 weeks, Senku states that now wine needs to be distilled into brandy, consequently failing to make a distillation through pottery.
After much trial and error, Taiju and Senku finally succeed in depetrifying a bird, with Senku saying Taiju is free to pick the first person they will depetrify thanks to his idea of making wine with grapes, with Taiju thinking his answer should be obvious.
Taiju and Senku reach the tree with Yuzuriha's statue, with Taiju shouting they can't revive Yuzuriha because she has no clothes on, only to be reprimanded for his naivety by Senku.
While arguing with each other, the duo is attacked by a pride of lions. Taiju wonders why the lions aren't attacking them immediately and why they are here in the first place, as Senku responds that they are probably the descendants of animals from the zoo and that they are careful enough not to attack an unknown target immediately.
However, it is only a matter of time, and Taiju claims he should sacrifice himself if the situation calls for it as Senku is more essential for society's survival. Senku then refuses this idea, and as they are cornered by the pride of lions they notice a statue of Tsukasa Shishio. They depetrify the statue, with Senku explaining the situation to Tsukasa. Tsukasa then quickly neutralizes the pride of lions and vows to protect them.
Tsukasa then asks them whether they posses any tools in order to use lion's meat, Taiju being surprised it can be eaten. After Tsukasa says that by making it food he is respecting the cycle of life, Taiju enthusiastically concludes that Tsukasa is not a "typical bad guy" and that he admires Tsukasa's point of view.
Taiju is next seen talking to Yuzuriha statues, asking her to wait for little longer while the group is making miracle fluid. While making more food, Senku inquires what the most important thing is for civilization, as Taiju brainlessly responds with "cellphone", irritating Senku and shocking Tsukasa. Senku then claims it's calcium carbonate - with Taiju suggesting they should be getting it from a gym storeroom, again provoking the same reaction from the pair.
Taiju is then tasked with physical work in order to acquire the said compound. He returns with materials, asking what the 4th purpose of calcium carbonate that Senku mentioned is, whilst Senku replies he said there were 3, after suspecting Tsukasa might have motives behind his compliments to Senku.
After Tsukasa and Senku have a falling out, Taiju runs to them with the pot containing miracle fluid, happily exclaiming they are able to revive Yuzuriha now. 
Senku supposedly claims the revival potion is just shy of the amount needed to revive a person, and says that he'll wait by playing siritori with Tsukasa while Taiju goes to the cave to retrieve the rest of it. Tsukasa suggests he should go, since he is the fastest, thereby taking Senku's bait. With Tsukasa gone, Senku checks once more if there is no sign of him, which Taiju confirms. The former then quickly orders Taiju to depetrify Yuzuriha while Tsukasa is absent. Taiju is surprised as to why Senku let Tsukasa go, as Senku explains that Tsukasa can't be trusted and that their ultimate goals will inevitably clash, therefore risking revealing cave's location in order to give them a grace period to flee with Yuzuriha. Taiju doesn't quesiton his friend's thoughts and concludes something must've happened between Senku and Tsukasa while he was retrieving the miracle fluid.
Since Yuzuriha isn't being depetrified right away, Taiju panics and wonders whether Yuzuriha is okay. Senku calms him down by saying the reaction takes time. Yuzuriha then promptly gets revived, as Taiju cries in happiness. Senku interrupts the emotional reunion by offering them a choice - either the two flee and live away from the conflict, or they fight to stop Tsukasa along with Senku.
Taiju responds by saying that if Tsukasa is breaking statues he will undoubtedly help Senku stop him, only to be cut by Tsukasa who arrives at the scene. Seeing parts of a statue crumbling from his hands, Taiju requests Senku look after Yuzuriha, while he assaults Tsukasa. Senku panics, thinking Tsukasa will kill Taiju with certainty seeing how he dispatched a pride of lions and shoots an arrow to land beside Tsukasa's head, only for Tsukasa to catch it mid-flight and spin-kick Taiju away. Tsukasa commends Taiju for withstanding his kick, saying that he's the first person to do so. He also notes that while Taiju could've struck him, he didn't and asks why that is - only for Taiju to say that he will not kick or punch him no matter how much beating he takes, and then orders Tsukasa to stop breaking the statues.
The group's silence is broken by a surprised Tsukasa who says there's no point to that statement, as there is no exchange for either party. Tsukasa then threates Yuzuriha's safety, imploring whether Taiju will attack him if he were to hurt Yuzuriha. After a brief moment of conflict, Taiju seemingly falls unconscious. After Tsukasa leaves, stating that he will keep destroying the statues that will compromise his ideal of the world, Taiju quickly wakes up. Senku then tells Taiju they are going on an adventure to make gunpowder, with Yuzuriha asking if Taiju should sleep to recover instead, only for Senku to say it was all a ruse to make Tsukasa believe Taiju will be out for a long time.
As Senku begins breaking various items in their makeshift house, a baffled Taiju and Yuzuriha ask why Senku is doing all this, with Senku replying they will make it look as they left in panic after Tsukasa scared them. With Senku noting gunpowder is necessary for Tsukasa's defeat, after he tells them that they need to go to Hakone, Taiju makes a suggestion to run to it in 5 hours in order to start making gunpowder, with Senku rebuffing him, saying that kind of feat is only possible for a stamina maniac like him. As Senku uses a sextant to mark the group's location, complaining about its accuracy, Taiju asks whether thereare any landmarks left - with Senku replying the time has washed them all away.
Yuzuriha then quickly notes that there are no tress in one of their directions, and the group runs to the tree free space - finding Karamura's Great Buddha and thereby pinpointing their location. As Yuzuriha begins crying when she sees the run down monument, Taiju cluelessly asks if anyone, including him, made her cry. Yuzuriha explains that she was not fully aware of the situation until she saw the monument. Senku comforts her by saying they will defeat Tsukasa and revive everyone caught in the disaster. Taiju then comforts Yuzuriha by saying Buddha has shown them the way even after all these years, with Senku saying it's simply made of bronze which doesn't decay like other materials. When Senku attempts to harvest some bronze out of the monument in order to make his sextant more accurate, Taiju immediately tries to goad him out of it, not to damage the sacred place.
As the group makes their way to their destination, Taiju notices a stone on Yuzuriha's toes, which is then erroded by the revival fluid. The trio finally arrives to Hakone, happily using its hotsprings to get some rest.
While they are at the hotsprings, Taiju informs Yuzuriha that he's been waiting the entire time under petrification to tell her something. Yuzuriha gets flustered and asks Taiju what it was that he wanted to ask her. Taiju responds with thinking about what he wanted to say for millennia, however actually saying it now when they are trapped in current circumstances and with no other options would be a coward's way out. Taiju then tells Yuzuriha to wait for him until they restore civilization, to which Yuzuriha agrees.
Taiju then recaps what happened so far to Yuzuriha - having revived Tsukasa, they only after found out he was a murderer and they promptly have to stop him. When Senku acquires sulphur and mixes ingredients in order to make gunpowder, he asks Taiju to start pounding it. As Taiju starts relentlessly pounding the mixture with a rock, a worried Yuzuriha asks if that will make sparks. Senku calmly explains that the rocks would have to contain iron to spark, being reminded that the rocks they are using indeed have iron in them - the group pulls away from the mixture as it explodes and gunpowder is confirmed to be made.
When Yuzuriha asks whether Senku really plans on using this on Tsukasa, Senku assures both Taiju and Yuzuriha that he will only use it to negotiate with him. The group then puts the fire out as they notice a smoke signal in the distance. Taiju inquires if it's a mountain fire and Senku replies it would be too coincidental for a mountain fire. Conflicted, Taiju asks Senku what to do. Senku decides to take the risk and light a smoke signal.
Taiju gleefly observes 3 smoke signals in response to their own. He goes back to Senku and Yuzuriha to inform them there are humans in the perimeter, only to hear Tsukasa's voice. Desperate, Taiju tries to rush through the woods to save his friends.He arrives in time to witness his friend being "killed" by Tsukasa. Taiju then charges in to recover his friend.
Taiju and Yuzuriha start breaking down in tears with his friend's corpse in his arms. Tsukasa tells them to get him a proper burial. Tsukasa assumes he has to be prepared for Taiju to attack him in a fit of rage even with Yuzuriha around, as Taiju rises with a huge boulder in his arms. He tells Yuzuriha he's calm with Yuzuriha nodding before telling him him she still believes the promise the three made long time ago and that everything will work out fine. Taiju agrees with this, throwing the huge boulder in the sky. Tsukasa suspects that Taiju is baiting him into observing the boulder instead of him, with Yuzuriha slipping from his eyesight and throwing a bottle of gunpowder at him. Tsukasa kicks the bottle and scatters the gunpowder, the boulder falling on it and sparking an explosion. As the smoke rises Taiju bids Tsukasa farewell.
Escaping from Tsukasa, Taiju attempts to revive Senku by using CPR. Yuzuriha warns Taiju not to move Senku's neck too much, stating that the reason for Senku's injury is because he sacrificed himself for her. Taiju then tells Yuzuriha that Senku would never commit suicide or sacrifice himself, instead looking for a solution which can save everyone. He makes an effort to remember whether Senku left a clue for the two of them. Yuzuriha remembers that Senku rubbed his neck while talking to Tsukasa, as if he was subtly inviting him to aim for his neck when killing him. Taiju recalls that he never had the habit of touching his neck and finds a small piece of stone that wasn't removed. The two then pour revival fluid on the spot, hoping that the reaction would revive their friend.
As the storm comes to an end, Taiju and Yuzuriha worry that Tsukasa might hear their voices, only to be interrupted by now awoken Senku congratulating them on figuring out his cues for the revival spot. Delighted, Taiju hugs Senku in his burst of happiness. Shortly after, Taiju comments on how the petrification that has caused everyone so much trouble can be used as a miracle replacement for a doctor in a world its left in such a regressed state.
Yuzuriha consults with Senku and informs Taiju they should go back to Tsukasa, much to Taiju's surprise. Senku explains that Taiju and Yuzuriha will serve as his spies now that Tsukasa believes he's killed Senku and they've nowhere to go. Taiju agrees to Senku's request, tearfully parting with his friend and hoping they meet again soon.
He and Yuzuriha contact Senku through their newly created phone. He is emotional over the call. When Senku plans to use a record of Lillian to make people defect to their side, he brings Nikki to talk, unaware that she is a Lillian Weinberg fan. She punches Taiju for every four letters he says, until he convinces her to come with them. Fortunately, Nikki decides to defect.
Later on, Taiju and Yuzuriha enter the woods and finds Senku. After a year apart, Taiju is happy to reunite with Senku. During this time, he meets the Ishigami Villagers for the first time.
He uses a satellite disk Senku has made to disorient Tsukasa's soldiers.
He aids in farm work. He is crowned King of Farming for his expertise. He aids in creating roads.
Soon Senku and the others recreate a motorboat, as they prepare to use it, Taiju spoke with Senku and believed the latter may have found a girlfriend because of the familiar smell. Taiju brought up Senku's love potion that Senku created thousands of years ago. This causes Senku to laugh, as he reveals that was merely gasoline, something Taiju is shocked to learn.
He is repetrified by Ibara and his crew. His body is thrown into the ocean. Taiju is depetrified to help lift Kaseki's petrified body. With help from Soyuz, he brings back the petrified bodies of the Perseus crew and a long haired stranger who he collects by accident.
He is petrified again by Ibara after the latter's crimes are exposed.
After Whyman's call, Taiju notes the latter can't be Senku and thinks the foe is using a recording. The next day, Taiju along with Soyuz bring up the unidentified statue. He watches the man being revived.
When the mentions of Senku's residual scars are made, Gen rallies every modern timer to recreate their scar using paint. At first, Taiju overdoes it and makes various lines on his face, as Senku has to tell him that his scar didn't resemble that. Soon Taiju recreated his facial scar, after Gen states it will serve as symbol, declaring the day they remove it will be when the threat is vanquished.
Taiju is on board the ship, taking part in the basic activities.
He is later excited to finally reach land.
Once on land, Taiju tells his restless and hungry friends that they can hunt wild animals, and wonders what sort of animals live in America, nonchalantly asserting that this is his first vacation outside of Japan. Minami is bemused about this, and Senku brushes it aside as part of Taiju‘s charm. After it is confirmed that America is still petrified, the crew are down but an excited Taiju tells them that they can revive everyone and Senku confirms this.
Taiju is later shocked to witness the new enemy has an aircraft. After Senku tosses Kirisame a way to bring the enemy down, Taiju uses body to act as a suitable surface for her and she successfully brings the plane down and the enemy escapes. On Senku's orders, Taiju cuts down the tree to collect the now downed plane.
When Gen listed Taiju as the science user of his colony, Taiju sneezed at that moment.he Perseus gets another call and Magma believes it’s Chrome but it is actually Dr. Xeno who has located the frequency of the group's communication. 
When the Perseus gets another call, it is Dr. Xeno who has located the frequency of the group's communication. Xeno requests to start negotiating with Dr. Taiju, something that leaves Taiju along with the crew confused. However, Senku realizes this was because of Gen and Taiju dresses up (despite it being a call) and talks with Xeno while being walk through by Senku on what to say. Xeno tells Taiju that his side has a clear technological advantage, with Senku telling the others Xeno has a factory that can produce mass amounts of ammunition. Taiju acts out that he knew this, as Xeno is none the wiser and Taiju's friends are impressed by his acting. Xeno makes them an offer to completely surrender and serve him since his manpower is lacking as he has no means to depetrify the statues. These words cause Ryusui to realize the enemy doesn't have revival fluid. Xeno also mentions that only those who have been aware during all 3,700 years can be revived with nitric acid alone, before questioning how he revived the statues thereby unintentionally confirming to the group he has no idea about the revival fluid. Taiju innocently attempted to answer Xeno's question about how to make the miracle formula, but he is stopped by Ryusui who along with Senku informs him they will simply crush the group once they have the manpower to do so. Senku states that they could have Corn City running with the formula. With this, Taiju rejects Xeno's offer and Xeno promptly ends the call. The group hear a noise and spot another plane, shocked the enemy had another one. The Perseus crew ask Senku on what they should do, as Senku states they’ll battle the enemy in the sky with their new vessels. Senku announces to the crew that he and Kaseki are building a runway for the Perseus.