The year is 2222, yet there are no hover cars, time machines, or other much expected novelties of the future. That is, with the exception of the Soul Foundry; a colossal tower where a new medical practice takes place—the transplantation of souls between bodies.

A schoolgirl named Manami lives in the town below the towering Soul Foundry. She has spent her summer vacation admiring Kazusa, a popular fellow classmate. However when the two finally meet, his hostile attitude completely turns Manami off, leaving her irritated that she was ever interested in him. One day, an accident leaves Kazusa in the care of the Soul Foundry, where his life is saved. However, his body requires a week of rehabilitation, which means his soul requires a temporary home. Unfortunately, the only option available to him is the body of a hamster.

Assigned as his caretaker, Manami reluctantly takes care of Kazusa in his new furry form. Yet as the week rolls forward, their bond begins to grow in a way the two hadn't foreseen, and brings to light a glaring issue: whether their relationship will have a future once they return to their normal lives.