Sarazanmai (Light Novel), Vol. 2

After accidentally breaking a statue of a mythical kappa, junior high students Kazuki, Toi, and Enta are transformed into kappa themselves as punishment by Keppi, prince of the Kappa Kingdom. Keppi has a task for the boys if they want their bodies back: work for him to hunt down zombie kappa born of twisted human desires. Even scarier, though? They're going to have to expose their own deepest fears and desires to each other to do so!