After a series of natural disasters that left modern civilization in ruins, Momoka and her grandmother now live in Japan. Her grandmother makes a living by selling obsolete technological devices while Momoka is tasked with the responsibility of scavenging through the wreckage to find valuable items. However, her job becomes more difficult due to the presence of a group of savage mutant oni who have claimed the area as their own. To win control of the valuable items within the wreckage trove, Momoka enlists the support of her friends - Monkey, Dog, and her loyal pet bird Kiji - and bravely confronts the oni in a battle.
