Astro is a robotic boy created by Dr. Tenma to replace his late son. When Tenma destroys his laboratory and shuts down Astro, the Ministry of Science revives him and tries to give him a normal life as a 6th-grade student who occasionally helps keep renegade robots from causing harm.

A lethargic student dozes through class, activities and pretty much everything, frustrating his best friend but attracting the affections of others.

Koyuki Tanaka's boring life is changed after meeting Ryusuke Minami, a local musician with a bad attitude, who introduces him to foreign music.

Luke fon Fabre, the spoiled son of a noble from the kingdom of Kimlasca-Lavaldear, has been confined inside his father's mansion ever since he was kidnapped seven years ago by a rival country, the Malkuth Empire. Now Luke's memory of the life he led before is missing, and a strange voice, which only he can hear, has been calling out to him ever since. One day while training with his mentor, Van Grants, a strange woman called Tear breaks into the mansion with the sole intent of taking Van's life. During the struggle Luke is transported far from home, along with Tear, and now that Luke has finally gained the freedom he's been dreaming of, what awaits him in the outside world will shatter everything he's ever known about himself.

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.

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.

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.

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.