Kokuyo is a middle-aged man with a large, muscular build, blond hair tied back in a ponytail, and a face marked by thick eyebrows, a prominent nose, and intense eyes. He is the former chief of Ishigami Village and the father of Ruri and Kohaku. As chief, he was strict, gruff, and deeply protective of his family and village, once even disowning Kohaku for her defiant actions. His primary motivation has always been the safety and well-being of those under his care, which initially made him highly skeptical of Senku Ishigami and his unfamiliar scientific methods. However, after witnessing Senku successfully cure his daughter Ruri of a life-threatening illness using antibiotics, Kokuyo acknowledged Senku’s capabilities and voluntarily stepped down as chief, naming Senku the new leader. From that point, he served as a co-leader of the village, focusing on practical matters like food gathering and physical defense while Senku advanced the Kingdom of Science. Kokuyo is a formidable physical combatant, skilled in using heavy rocks and his natural strength in battle, though he has no scientific expertise. His role in the story evolves from an initial antagonist figure of tradition to a steadfast supporter of the scientific revival effort. Throughout the events of Dr. Stone: New World, he continues to protect the village and assist in larger expeditions, remaining a loyal and pragmatic presence. His relationship with his daughters is central to his character; he is especially close to Ruri while his bond with Kohaku is tested and eventually strengthened through mutual respect. Kokuyo’s development reflects a gradual shift from rigid tradition to openness, valuing results over custom when the survival of his people is at stake.