The story takes place in a city called Ioluf, where people born here have infinite lifespans, but their appearance is frozen at 15 years old. Maquia (voiced by Iwami Maiaka) is such a native Ioluf girl. One day, in order to snatch the blood of immortality, the Mesati army launched an air strike on Ioluf on ancient mythical beasts, causing heavy losses. Maquia's friend Lelia (voiced by Kayano Ai) was abducted, and with Lelia, the boy Maquia secretly loved, Krim (voiced by Kaji Yuki). In the dark forest, the surviving Maquia picked up a baby boy whose parents died in the previous attack. Maquia adopted him as a mother and named him Ariel (voiced by Irino Miyu).