One day, Yuuichi, the main character, contracted a disease that causes his penis to become too energetic and "produce a lot of semen.

According to Yoriko, a female doctor at a nearby hospital, the cure is to ejaculate. Yuuichi asked Yoriko to teach him how to masturbate, and she decided to help him ejaculate by squeezing his penis for the time being.

However, it seems that so much semen is produced that she has to squeeze it every day, and Yuuichi becomes worried about his erect penis.

One of the neighborhood mothers becomes suspicious of Yuuichi's unusual behavior and asks him about his penis. Yuuichi thought that she would hate him for having such a disease, but she was willing to help him with the treatment....

[from official site]