I would consider this a deconstruction of netorare. The guy likes the girl but finds out she’s a slut fucking tons of other guys. But it’s not like she’s mindbroken or the guys are malicious: they’re all fucking in mutual agreement because they’re enjoying themselves. The guy also realizes that he never really loved the girl, but was just sexually attracted to her. He has the opportunity to go back to her, but decides it isn’t worth his time and lets go of his affection gracefully.