I like of get what they are trying to sau but it feels like the women somehow stumbled into another man's dick in her own apartment.
I would have felt better if Yuu was a hard working man who worked nights and he found his wife in a bar drunk and being hit on by stranger and then follow them to HIS apartment.
I would have accepted it like: Okay, he is drunk, unhappy, she got taken to his apartment (probably a lie) and the hero was afraid to confront them.
This ending? It feels like she cheated on him, brought the cheater to THEIR house. Etc.
Now, instead of the MC having only gone on a journey to improve himself and relationships and sex.
Now it feels like the MC went on a mission to learn to excuse cheating by doing a lot of cheating (because even though he was cheated on, he still cheated because he was thinking/loving his wife). And he basically learned: if I can become the most experienced master of sex, then no woman is ever going to find someone better than me.