Years ago, when the Chaos Cult summoned the God of Destruction, Magu Menueku, a devastating battle broke out with the fate of humanity hanging in the balance. In order to save mankind, the honorable Holy Knights sealed Magu into a Holy Sealing Crystal.

Eons pass until Ruru Miyanagi, a happy-go-lucky middle school student, stumbles upon the crystal while digging for clams. She unintentionally releases Magu, waking him from his long slumber. But instead of cowering in fear, Ruru is eager to befriend Magu, even dubbing the God of Destruction "Magu-chan!"

Magu finds himself at the mercy of this young girl as he attempts to regain his full powers—not to mention his bigger and "badder" form. However, as Magu progresses in his mission, his friendship with Ruru blossoms as he learns a bit more about the lowly world he plans to destroy.