Saeki has been with his girlfriend for three years. She sees their future only in terms of marriage and comfort. He is an ordinary office worker with financial difficulties and a boring life. His only escape is secret dates with his boss, Misaki, who irritates him to the point of grinding his teeth. Her perfection, her unbridled drive for success and her willingness to help colleagues, even when they make mistakes, constantly remind him of his own dullness. One day, in a dark alley, he loses control and pins her against the wall, forcing her to take off her mask. But Misaki doesn't pull away — she steals a kiss herself. Thus begins their secret romance. Sex with Misaki is sweet and intoxicating — completely unlike what he experiences with his girlfriend — and gradually it consumes Saeki completely.

(Source: Ryona-sensei)