Society's view on cheating is so unbelievably fucked. Its as if the scale of moral wrongdoers goes 1. Hitler 2. Stalin 3. Cheaters 4. All other wrongs, I swear. Unironically the husband of the girl he cheated with was doing way more fucked shit than anything the MC did in this manga. That level of obsessive control over your partner to the point where he'd install cameras in her fucking apartment is insane. Also, the college friend character raped girls. The fact that he felt the need to punish himself as hard as he did is sad.