Kohaku (コハク) is a young woman who is a descendant of modern humans. She is Ruri's younger sister and the daughter of Kokuyo. She is one of the protagonists of the series.

After Taiju, Kohaku is the most loyal to Senku. Since learning about science and delicate/complicated work it takes to make modern inventions, Kohaku often teams up with Chrome to scavage ingredients and "persuade" Kinro and Ginro to help with the labor.


Kohaku is a young woman of average height with a slim-but-curvy figure, a delicate face, blue eyes, and blond hair tied-up in a spiky ponytail. Her appearance is that of someone who appears to be a mixed heritage of American/Japanese, denoting her heritage as the descendant of Ishigami Byakuya and Lillian Weinberg. She shares a resemblance with her older sister, Ruri, but has wild hair in comparison to her sister's soft, flowing hair, and a slimmer body. Her clothing consists of a crude, navy blue dress with a rope tied in the middle, and uniquely shaped stone sandals.



Kohaku is a kind young woman, caring deeply for her sickly older sister, willing to participate in the tournament for her hand in marriage just to protect her. This care extends to her comrades, and anyone she's loyal to. In addition to this, she has a reckless and hotheaded personality, often reacting in anger to being called a gorilla or lioness due to her strength and physicality. She also acts on her emotions at times, going against rational thought and rushing in. Kohaku also has a bit of a teasing side, asking Chrome if he could fall for her to her resemblance to her sister.

She's repeatedly impressed by Senku's scientific creations, although at first, it took her a while to accept that it's not simply magic.

Kohaku excels at fighting, hunting, and general survival skills. She is a tomboy by nature, having little interest in more typical feminine activities and has little knowledge about them, although she does seem to enjoy some lavish clothing that was provided to her. Kohaku has no problem with being around boys while swimming or changing clothes; she will, however, retaliate if a boy stares lustfully at her breasts. She possesses a sharp instinct and intellect.

During the early part of the story, Kohaku tends to be a hair-trigger away from attacking people she distrusts. Such was her first impression of Gen, who admitted to being initially a spy for Tsukasa; she even attacked Tsukasa himself without really knowing why he attempted to kill Senku. Thanks to Senku's numerous scoldings and encouragement to think more than one step ahead, Kohaku grows out of this habit, but her temper is still a problem.

Perhaps because of her instinct, Kohaku seems to be a good judge of character. She was able to deduce that Gen was the kind of person who, despite being able to lie without batting an eye and claiming to only work for his self-interest, cherished his loyalty and friendship with Senku. She also recognized that Chrome was in love with Ruri, but hadn't realized his own feelings yet, and was able to read Senku's personality to an extent.

Similar to Senku, she doesn't seem to be interested in romance, previously claiming to have fallen for Senku when she meant that she found him interesting as a person. It was stated that she had feelings for Chrome in some ways, she asked if Chrome would accept her as his wife as she and Ruri look alike. She has shown to hate shallow or selfish men, at first disliking Gen for wanting to switch to Senku's side due to the apparent benefits switching would reap. However, Kohaku later describes the kind of man she's into: "Men, who for what they believe in, will keep putting one foot in front of the other, for all eternity, chipping away at progress."[4]

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 possesses great strength and endurance, credited by Chrome to be one of the few superhumanly strong individuals within the village, being able to carry a heavy pot filled with hot water on a daily basis for her sickly older sister, Ruri. But her more notable traits are her speed and agility, which makes her highly proficient in close-quarters combat. When fighting, she attacks with a flurry of blades and kicks. She also possesses quick reflexes, as she was able to easily stop an attack from Kinro and Ginro when they both attacked her. In addition to all this, Kohaku is gifted with incredible eyesight, being able to spot Tsukasa and Senku from afar, and finding oil from just the aerial view of the hot air balloon and a map.


Kohaku is an accomplished hunter. She caught a wild boar for Francois with ease when they were looking to capture some for their farm. She's one of the most reliable people when it comes to hunting. Additionally, her extraordinary eyesight helps in all these endeavors.


Perhaps because of her experience in hunting, Kohaku possesses a sharp instinct, able to discern information and situations correctly.


While not as smart as Chrome or skilled as Kaseki, she proves to be quick on the uptake in understanding of some of the science Senku demonstrates, and the complex strategies they use in their endeavors, like her covert acts to send Senku supplies and critical information despite the lack of 2-way communication and her illiteracy.

When Ginro was severely wounded, she realized to save him, she would have to petrify him and using that tactic, her plan was successful.


Kohaku wields two primitive-looking knives and an orange-colored buckler. Later, she discards her dual knives in favor of the katana that Kaseki and Senku forged for her and the other warriors.


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


  • Her name Kohaku is the Japanese word for Amber, which 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.
  • She is the first girl to kiss Senku.


  1. 1.0 1.1 Dr. Stone Manga; Volume 4, Q&A Section
  2. Dr. Stone Manga — Chapter 121, Kohaku is Petrified along with Ginro.
  3. Dr. Stone Manga: Chapter 138
  4. Dr. Stone Manga: Chapter 121, Page 4


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