The interplanetary spacecraft Galileo II carries Atom and his friends to Titan, a satellite of Saturn. However, what awaits them when they arrive there is an attack from an unknown entity. What appears is a mechanical life form called "Igza" that wants to destroy humans. The battle between Atom and Igza unfolds in the far reaches of space.

Atom is attending a party on the space station with Dr. Ochanomizu. However, while at the party, he hears a voice. It is the voice of a robot that had been abandoned by someone. The abandoned robot is a security guard robot named Ivan, and after being refueled with energy, Ivan sets off on a journey to find his owner, Minya.

Doctor Tenma, chief of the Ministry of Science, brought a digital brain genome from an aircraft. Doctor Tenma begins a trip to Mars, then combines the genome with a robot. Doctor Tenma's son, Tobio, who had died in a traffic accident, has been revived.

A boy is chased by a robot through some ruins. There, he finds an Earth ruled by a computer called "Gaia," who has lost patience with humans who repeatedly cause war and environmental destruction. While desperately trying to escape, the boy discovers Atom, which had been put on display 200 years ago after it had finished its role.