Hiroki is a human boy whose forgetfulness leaves his coin purse unzipped, costing him 500 yen. This mishap brings him into contact with Chuck Shimezō, a young trainee zipper yōkai. Discovering their mutual exasperation with nagging mothers, the two forge a bond over shared family frustrations.

Driven by a mutual desire to escape their home lives, Hiroki and Chuck resolve to run away together. Their goal is to reach Hiroki's grandfather's home. Their departure takes an unexpected turn when Hiroki's sister, Chie, joins them. Now a trio, Hiroki, Chuck, and Chie journey towards the grandfather's place, navigating the complexities of their runaway plan.