One day in early summer, the protagonist finds used sanitary napkins stuffed in his slippers.
Four girls appear in front of the confused protagonist. Saori, Mami, Youko, and Yuuko.
A group of bullies at the center of the class.
They force the protagonist to lick the used napkins. It is the first time he licks something that was in close contact with a girl's private parts before.

After that, they start to bully the protagonist. They make him swallow their drool in the classroom, and pee in the girl's toilet.
What's more, they give him the nickname "Girl's Toilet". He has to lick the panties of all girls in the class, the bullies pour pee on him,
he has to swallow it, and the pee-rich bullying continues...