Kohaku (コハク) is a young girl and a descendant of modern humans. Ruri's younger sister.


Kohaku Full Body

Kohaku Anime Profile

Kohaku is a young girl with a delicate face and tied-up blonde hair. When her hair is untied, it is shown to be massive cowlicks. Her clothing consists of a black dress(navy blue in the anime) and uniquely shaped stone sandals. Tsukasa remarks her appearance as half American-Japanese, implying that she's the descendant of Lillian and Byakuya.


Kohaku is a tomboy who excels at fighting, hunting, and general survival skills. She has little interest in more stereotypical feminine activities and has little knowledge about them. As a hunter, she has keen instincts, being able to tell when someone is a threat and be on high alert, reacting instantly. In addition, she seems to be a good judge of character, being able to tell that Gen was the kind of person who could lie without batting an eye and that in spite of claiming to only work for benefits, is merely too prideful to admit his loyalty and friendship with Senku. She similarly understood that Chrome was in love with Ruri but hadn't realized his own feelings, was able to read Senku's personality to an extent (including his use of science to "bait" people to his side), and accurately predict Ryusui's response to being revived a second time. While she is very tomboyish, she is insulted when people call her a gorilla or lioness (though admits she prefers being called a lioness over a gorilla). The only person to get away with this without being hit by her is Senku, whose intelligence, charisma, and innate kindness she deeply respects. Similar to Senku, she doesn't seem interested in romance, previously claiming to have fallen for Senku when she meant that she found him interesting as a person. However, she has shown to hate shallow or selfish men, instantly hating Gen for wanting to switch to Senku's side due to the benefits and prefers gentlemen like Senku.

She's repeatedly impressed by Senku's scientific creations, even though it takes her a while to accept that it's not simply magic. However, she has a short temper that causes her to be angered easily at the slightest insult to herself or her friends. She can be emotional and impulsive, allowing her feelings to get in the way of her rationality and cause her to act rashly without thinking of the consequences.

She cares deeply about her older sister Ruri and tried to alleviate her chronic illness no matter how physically demanding the task. As she didn't want her sister to be married off to the winner of her village's tournament, she strove to become Ishigami Village's strongest fighter. This care extends to everyone she considers her friends. She was extremely angered to see the Treasure Island tribesmen petrify her friends, shatter their stone bodies, and throw them in the ocean. She is very kind having attacked Tsukasa for murdering Senku whom she considered a gentleman for his actions in saving his friend Yuzuriha, despite not knowing the two at the time. She also demonstrates a mildly mischievous personality, teasing Chrome about his feelings for Ruri and if he would date her instead since they looked alike.

Abilities and Skills

Kohaku appears to be well known in her village due to her combative abilities, as both Kinro and Ginro were afraid of her. Tsukasa, a world class fighter, stated that she would have been famous for her fighting abilities back in the Pre-Petrifaction world.

Physical Abilities

Tsukasa vs Kohaku

Kohaku's swift strikes.

Kohaku is very fast and agile, being able to attack with her knives and legs swiftly. Her strength and endurance are also remarkable, being able to carry a heavy pot filled with hot water on a daily basis. She is also fast enough to dodge a bolt of lightning. Chrome referenced her as one of the few members in her village with superhuman strength, while also being very nimble and agile. She is incredibly proficient in close-quarters combat and was able to easily stop an attack from Kinro and Ginro with her quick reflexes. Kohaku also possesses incredible eyesight, being able to spot Tsukasa and Senku from afar.

Master Hunter

Kohaku was an excellent Master Hunter. She can easily catch boar with ease when Francois, Ryusui's butler is looking for a boar to farm and try to catch it using a trap. She's one of the most reliable people when it comes to hunting. Additionally, her extraordinary eyesight allows her to spot oil fields from an aerial photograph.


While definitely not as smart or skilled as Chrome or Kaseki, she proves to slowly be understanding of some of the science Senku demonstrates. She can be clever and quick on the uptake and demonstrated at least some ability to multiply in the Arithmetic Battle bonus though she is illiterate. In addition, during the Treasure Island arc, she showed the ability to understand the situation and act covertly to get Senku supplies and understand what was important to gather and give to Senku.


Kohaku wields two primitive-looking knives and an orange-colored buckler. She appears to be very skilled in using those during combat. After forging a katana, she discards her dual knives and starts using the sword instead.


3/5 C
5/5 A
3/5 C
2/5 D
Kohaku's stats, according to Volume 6


Kohaku was born around 3,700 years after the mysterious petrification incident.


Vs. Tsukasa Arc

She is first briefly seen, tending a fire.

Science Kingdom Arc

She witnesses Tsukasa take Yuzuriha hostage and nearly kill Senku and later attacks him. Tsukasa traps her under a tree and she is saved Senku, using a pulley. She decides to take him to her village.

Village Games Arc

She helped Senku win the village games to protect her sister Ruri from Magma.

She is careful with the things in making the "cure all".

Vs. Hyoga Arc

She is almost stabbed by Hyoga, but is saved after Gen sabotaged his weapon.


  • Her name Kohaku is the Japanese word for Amber is also a fossilized tree resin.
  • In the cover of Chapter 17, her eyes were mistakenly shown as yellow/brown, even though it was stated that she has blue eyes. This mistake was later fixed with the cover of Chapter 22.
  • Kohaku ranked 2nd in the 1st Character Popularity Poll.
    • She was close to rivaling with Gen, who ranked third place.


  1. Dr. Stone Manga; Volume 4, Q&A Section
  2. Chapter 99


v  e
Kingdom of Science
Male Taiju OkiSenku IshigamiGen AsagiriChromeKasekiKinroGinroMagmaRyusui Nanami
Female Yuzuriha OgawaRuriKohakuSuikaNikkiMinami
v  e
Post Petrification Humans
Male ChromeGinroJasperKasekiKokuyoKinroMagmaMantleSoyuzTetsuken
Female GarnetKohakuRubyRuriSapphireSuikaShiroganeShovelTurquoise
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