A murder takes place in the town where Kenta Ochiai lives. The mutilated body is found by the riverside and Kenta, an elementary school boy, sees a crocodile swimming in the water. Being labeled as a liar in class, he decides to capture the creature with his friend. Was the body mutilated by the crocodile or the murderer? All connections lead to the riverside involving his teacher, parents and a girl practicing her trumpet across the river.