Chibi Maruko chan is the nickname of a sweetly obnoxious 9-year-old girl. She tricks her grandfather, ponders for hours over how to spend her allowance, and hates sitting next to ugly boys. She talks, feels and lives just as real kids do. As the second term commences, Maruko and her classmates return to their small groups. Maruko’s group includes two naughty boys and Maruko is forced to be one of their subordinates. She seems to face a lot of pressure at school.

After hitting a passing spaceship and causing it to crash, a troupe of aliens and robots rescue the only survivor. It is a human baby named Corona that they decide to raise on their own, using the data they retrieved from the computer to mimic the life she would have had on Earth.

As the Overfiend slumbers, the mad emperor Caesar rises to power, enslaving a new race of demon beasts. Into this cruel existence is born the Lord of Chaos, the Overfiend's nemesis. As the blood-thirsty beasts capture the tyrant's daughter in a brutal coup, the Overfiend must awaken to an apocalyptic battle of the Gods.