alternate name: 僕は彼女の浮気を知っている The Motion Anime.
The heroine Sae Yamanaka and the main character Hiroshi have been in love since childhood.
Since Sae is currently attending a university far away, they are in a long-distance relationship.
One day, when Hiroshi went to her house and he heard Sae’s gasping voice.
She is having sex with a man other than himself. Hiroshi was shocked to be betrayed but at the same time, he was struck by a powerful excitement he had never felt before.
“With what kind of expression and gesture would she accept a man other than himself?”
“I want to know. I really want to know what kind of sex you have with a man other than myself.”
Driven by distorted desires, Hiroshi finally takes action because he wants to see his dear girlfriend cheating sex.