Igarashi Natsu is the soul of Dr. STONE ’s second half. He is the reminder that beneath the blueprints and the chemical reactions, science is a human story. It is the story of children waiting for their parents, of communities preserving stories, and of frightened young men finding the courage to face the cosmos not because they are unafraid, but because they love. In a series that often celebrates the cold logic of the laboratory, Natsu stands as a warm, beating heart—proof that the most essential element for rebuilding civilization is not just intelligence, but empathy. He is, without question, the most human character in a world of stone.

He also serves as a foil to the series’ antagonists. Unlike Tsukasa, who sees the old world as corrupt, or Ibara, who sees only power, Natsu sees a continuous line of human value. The past (his parents, the astronauts) is sacred. The present (his friends, his village) is precious. The future (the moon mission) is hopeful. He reconciles these three tenses of time through the simple, radical act of caring.

In the grand tapestry of Dr. STONE , a manga and anime series that glorifies human ingenuity and the relentless march of science, it is easy to be dazzled by the pyrotechnics of Senku Ishigami’s intellect or the raw power of Tsukasa Shishio. Yet, woven into the fabric of the series’ second major arc—the “Age of Exploration” and the journey to the other side of the petrified world—is a character of quiet but profound importance: Igarashi Natsu. Often affectionately called “Soyuz” by fans (a reference to his ersatz role as a Soyuz spacecraft commander), Natsu is more than just a brawny crew member. He is the living conscience of the new stone world, a bridge between the primal fear of the unknown and the scientific courage required to face it. The Heir to a Burden: Introducing Natsu When the crew of the Perseus first encounters Natsu on the shores of North America, he is presented as a dichotomy. He is physically imposing—a son of the formidable warrior Kohaku—yet his demeanor is gentle, uncertain, and deeply melancholic. He is not the brash, confident fighter one might expect from the Ishigami Village bloodline. Instead, Natsu carries the weight of a broken promise and a lost past.