In 2015, Dr. Yamanoue, the Secretary of the Ministry of Science, devoted himself to constructing an android on a man‑made island. He intended to raise the machine as if it were his own son, but the robot"s circuitry was defective. Realizing that Dr. Kawashimo"s expertise would be essential to fix the flaw, he sought his help. Though they are friends, their rivalry extends into both personal life and scientific research. Yamanoue is fiercely nationalistic, seeing the robot only as a strategic asset, while Kawashimo is a pacifist who cares deeply for machines.
Responding to Yamanoue"s summons, Kawashimo hurries to the island with his young daughter Miri. Upon arrival he installs an electric brain into Jet Mars, a boy‑robot, bringing him to life. Mars is bewildered by everything; he cannot tell right from wrong. The next day he lifts Kawashimo and Miri onto a structure, noticing a glimmer of moisture in Miri"s eyes that stirs an uncanny feeling within him. He asks Yamanoue about it, and is told that tears are shed by weak girls, while a strong man never weeps.
One day the electric core of another robot, Fainton, fails, causing it to go berserk and plunge the island into chaos. When seawater floods the facilities through a massive breach created by Fainton, only Mars remains astonished and unsure of what to do. At that moment Miri displays her extraordinary power, sealing the breach. Guided by her, Mars carries an iron plate and repairs the damage. Together they rescue Yamanoue and Kawashimo from drowning. Miri, crafted by Kawashimo, teaches Mars how to cry and perform acts of kindness.
Madhouse Studios 
Toei Animation Japan