Based on the erotic game by TinkerBell.

One day, Yamato, Mikoto and Takeru visit a village in the mountain for the training to be monster hunters. They have various hard trainings and finally become the monster hunters. But there is something wrong with Yamato's body. His body gradually changes into a monster... what is happening to his body? Who can stop it? To save Yamato, Mikoto and Takeru make every effort to do so. What is the secret to Yamato's body? What will happen to Mikoto and Takeru?

(Source: ErogeShop)