A Japanese boy moves to a town in Russia after being adopted by his father ex-girlfriend, known there as "the lady of the Mountain". But who is this woman? What powers is she hiding?

16 years ago, Japan was swept by a series of natural disasters that destroyed all modern society. Momoka lives with her grandmother who makes a living selling pieces of the old technology. It's Momoka's job to dig up the "treasure" from the junk yard. But, things get harder since some punk mutant(?) oni claim the junk yard as their own. The battle is on as Momoka battles the oni for a piece of the action with her friends Monkey, Dog, and pet bird, Kiji.

An extremely normal boy meets a demon while looking for a missing cat.