Watashi, a single office worker living in a Tokyo apartment, originates from the mountainous Okuyoshino region of Nara Prefecture. His childhood there involved growing up alongside a kappa, fostering a lifelong affinity for the creatures. During his commute home one day, he spotted a water kappa in a pet shop window and purchased it impulsively. He named the kappa Kaatan and committed to raising it.

With no prior kappa-care experience, he depended heavily on instructional books titled "How to Raise a Kappa" for training and daily routines. Training Kaatan presented ongoing difficulties, as the kappa frequently ignored commands or forgot lessons. Despite these setbacks, he persisted with unwavering patience and dedication, constantly refining his approach.

He developed romantic feelings for Ms. Sakamoto, the pet shop employee who sold him Kaatan. She shared his passion for kappas, conducting experiments and maintaining detailed observation logs. Their relationship progressed when she traveled to his rural hometown for a kappa-related medical need and grew enchanted with the area. She relocated there, left the pet shop, and later married him.

While raising Kaatan, he remained resilient and studious, regularly consulting reference materials to overcome new challenges. His daily life centered on understanding kappa behavior and ensuring Kaatan’s welfare, embodying his persistent and nurturing disposition.