A young man named Watashi, upon passing by a pet shop on his way home, happens upon a water Kappa in the window, which he buys, names Kaatan, and is determined to raise as a pet. Never having owned a kappa before, he relies on a book that specializes in information on how to raise and train kappa. However, Kaatan is harder to train than it immediately seems, and a lot of patience is exerted by Watashi in his effort.

A young man named Watashi, upon passing by a pet shop on his way home, happens upon a water Kappa in the window, which he buys, names Kaatan, and is determined to raise as a pet. Never having owned a kappa before, he relies on a book that specializes in information on how to raise and train kappa. However, Kaatan is harder to train than it immediately seems, and a lot of patience is exerted by Watashi in his effort.