Ep. 52: Astro Boy retrieves a blueprint from Grota Republic and bonds with Nuka, a robot girl containing a neutron bomb.

52

In a prologue, creator Osamu Tezuka reveals that Astro Boy’s legs belong to a robot girl. The episode explains that Astro is sent to a Grota Republic military fortress to recover a blueprint template. There, he meets Nuka, a sentient robot girl constructed from that same template, which includes an integrated neutron bomb. To prevent detonation, Nuka must be dismantled. Astro, who has developed feelings for her, remains by her side until the end. Only her legs remain after the sacrifice. Astro brings them to Dr. Elefun and requests that he replace his own legs with hers, ensuring she remains part of him permanently. Elefun complies with the request, allowing Astro to continue his adventures with her legacy intact.