Based on the erotic game by Jitaku Studio.
Our protagonist, Tooru Seo, writes down all the situations he fantasizes about in a notebook he calls his "sexual fetish diary". It's a form of self-pleasure that suppresses his overflowing sexual desire, and is an alternative to masturbation! He thought that no one would understand this hobby, and that he'd never be able to get a girlfriend. One day, Tooru forgot...