In a distant future, humanity has relocated from Earth to a colossal ring structure encircling the planet to safeguard it. This ring society is tiered by floor levels, with status increasing higher up. Mitsu, a humble boy and son of a window washer, completes junior high only to face his father's sudden disappearance. Forced to inherit his father's job, Mitsu grapples with this new responsibility. Through his work, Mitsu gains a unique perspective into the miniature worlds within the Saturn Apartments, offering him a glimpse into diverse lives and narratives.