Ayumu Aikawa, a 16-year-old high school student, is tragically assassinated while looking into a suspicious residence. He soon awakens, though, next to a weird armored female named Eucliwood Hellscythe. She exposes herself to be a necromancer who has resurrected Ayumu, transforming him into a zombie! Ayumu, now immortal, sets out to find his murderer. One day, while hunting in a cemetery, he comes across Haruna, a lively little girl dressed as a magical girl who is fighting a bear with a chainsaw. Haruna tries to erase Ayumu's memory of her when she kills the beast, but he instead takes her magic for himself. Haruna, stripped of her abilities, now instructs Ayumu to take over her task of hunting weird creatures known as "Megalo," monsters that roam the human world and terrorize the population.