'Saki' cares about her younger brother 'Mamoru' who has not been feeling well lately. According to the story, Mamoru, who still doesn't understand the meaning of sex, is being bullied at school. Saki answers Mamoru's depressed question. Saki tells her that she can't have sex with her siblings, but after an incident that happened at school with Mamoru, Saki decides to go out of her way to help her cute little brother.
