When Toru's penis suddenly starts growing, he has no understanding of his own body. Completely unaware of even the term "erection," he becomes anxious as his cock keeps getting bigger and bigger. Worried he might be sick but unable to talk to anyone about it, he reluctantly seeks help from the school nurse. However, the nurse is actually a pervert with a secret attraction to young boys. Under the guise of medical treatment, he begins sexually molesting the boy—licking his immature cock and stimulating his virgin anus—quickly turning their relationship into something deeply sexual. Are these acts really treatment, or just pure pleasure? Caught in this twisted situation, Toru is overwhelmed by fear and confusion as he's drawn deeper into the nurse's depravity.