Maboroshi (2016)

When a body is discovered murdered by the river in Kenta Ochiai's town, the elementary school boy witnesses a crocodile swimming nearby. Already distrusted by his classmates, Kenta teams up with a friend to capture the creature. But was the crocodile responsible for the body's condition, or is a human killer at work? The investigation pulls connections to the river involving Kenta's teacher, his parents, and a girl who practices trumpet on the opposite bank.