Nordic mythology is not fiction, but ancient history sealed by the world tree "Yectrasil". Modern human civilization was rebuilt on the ruins of the Nine Realms. A few humans have the blood of the Asa, Vanir, or giants. They are the "descendants of gods."
"Valhalla Academy", a secret organization composed of gods, appears to be an elite school for nobles. It is actually responsible for hunting down monsters that escape from the cracks in the World Tree and preventing Ragnarok from happening again.
The world tree is still withering, and the prophecy is being fulfilled:
When Loki's son breaks free from his chains,
When Baldur, the god of light, died,
When Fenrir swallowed the sun,
Ragnarok will come again.
The key to everything is a "bad kid" chosen by fate.
