The story takes place in a future where after a great conflict the planet was devastated, after this military weapons was outlawed and the command given to an independent authority in the 6 remaining regions.
The anime's opening theme is "Spell" by Lama and the ending theme is "Rokutou Sei no Yoru" by Aimer. The story takes place in one of these areas, the city No. 6. Shion, a boy, was found at the age of two years as a being with an extremely high intelligence that allowed him to live in a luxurious area called "Cronos".
