Upon seeing a kappa in the window of a pet store on his way home, a young man makes an impulsive decision to purchase it and names it Kaatan. Despite having little experience as a kappa owner, he invests in a guidebook to nurture and train the creature. The guidebook provides valuable advice, but implementing the tips proves to be a challenge for the owner. Though Kaatan grasps the concepts initially, he frequently forgets them and loses interest. However, the determined man remains patient and persists in his quest to transform Kaatan into a well-behaved pet that he can be proud of, although the chances of success are uncertain.