The character Astro Boy, which was called “child of science” in the 1963 anime series, is related here to Imperial Japan’s wartime policy of science. The term “child of science” was also applied to other characters at the time of the Asia-Pacific War, and intriguingly, the use of it covered not only mechanical but also human children. Seeking to find answers to the question of how such different things could be subsumed under the same term, the focus is on the empire’s policies and discourses of scientific warfare, and how they transformed children’s media of entertainment and education – manga, magazines, toys, and music – and even children’s bodies into weaponry at perceptual and physical levels. The issue of the “weaponization” of human bodies helps to reconsider the military traits and the subhuman qualities of Astro Boy. Extending this to Imperial Japan’s history of child soldiers, and conducting both intratextual and transtextual research of related anime and manga by Osamu Tezuka, this study brings to light the unnarrated life of Tobio, the human original of Astro Boy, as well as the implication of his premature death.