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 meeting Senku and witnessing his bravery, courage and talent, Kohaku invites him to her village. Since Senku assists and fascinates the village with many of his scientific inventions and turned out to be the savior the village ancestors talk about in the stories that are passed down, the population is ultimately rallied to fight and stop Tsukasa's tyrannic empire.[15] After Taiju, Kohaku is the most loyal to Senku. Since learning about science, and the delicate, complicated work it takes to make modern inventions, Kohaku often teams up with Chrome to scavenge ingredients and "persuade" Kinro and Ginro to help with the labor.