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.
This is a crucial narrative lesson. Senku’s courage is born of certainty and knowledge. Kohaku’s courage is born of physical prowess and instinct. Natsu’s courage is born of love . He fights not because he knows he will win, but because he cannot bear to live in a world where he did not try to save his family. His decision to board the Soyuz capsule during the final launch preparations—not as a commander, but as a son sending his parents a message—is one of the most quietly heroic moments in the series. He proves that emotional strength is as vital as physical or intellectual strength. By the end of the series, Igarashi Natsu does not become a famous scientist or a legendary warrior. He remains a farmer, a guardian, and a man of deep feeling. But his role is foundational. He represents the purpose of the Kingdom of Science. All of Senku’s rockets and revival fluids are ultimately meaningless if there is no one to care about the people being saved. Natsu is the emotional core that prevents the series from becoming a cold, procedural textbook. igarashi natsu
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. He also serves as a foil to the series’ antagonists
When Senku and the team arrive, they do not mock this facade. Instead, they validate it. Senku, in his typical pragmatic fashion, uses Natsu’s local knowledge and his emotional connection to the rocket as a tool for their mission. But in doing so, Senku inadvertently offers Natsu the greatest gift: purpose. By helping to repair the real Soyuz and plan the journey to the moon, Natsu is given the chance to turn his childhood play-acting into genuine heroism. He moves from being a boy waiting for his parents to return to a young man building the vehicle that will bring them back—or finally confirm their fate. One of Natsu’s most critical functions in the narrative is as a keeper of oral history. In a world where books have turned to dust, the memory of the old world is fragile. Natsu, raised on stories of the astronauts and the petrification event, represents the human chain of memory. He is the living link between the era of spaceflight (Byakuya, Lillian, Shamil) and the era of reconstruction (Senku, Chrome). The present (his friends, his village) is precious