Misao is a little bit quiet and shy. When she practices swimming at school, a big explosion strikes. And she is attacked by mysterious monsters. The monsters sneak into her body, and she loses her consciousness. When she wakes up, there is nothing changed in her body. Is that a dream? Several days later, she suddenly gets seized with an irresistible impulse to have sex. This happens because the monsters inside her long for semen. She tries to suppress it, but the impulse gets stronger day by day. Her patience is about to run out. Breaking relationships with friends, the growing impulse and the monsters. Will there be an end to her agony...?