Kappa no Sanpei

A seven-year-old boy named Sanpei is often mocked by his classmates for his appearance, but he remains cheerful and content living with his grandfather in the mountains. He is more interested in eating his school dinners than paying attention to anything else. When his school announces a swimming competition offering a trip to Tokyo as the top prize, he decides to participate, hoping to see his mother who has lived there for years. As he is not a strong swimmer, he practices in a nearby lake, only to be pulled under by a current and drown. He awakens in the magical world of the Kappa, where he meets a Kappa child named Gartaro. There, he begins to uncover the truth about his mother and the mystery of his father's disappearance.