Dude has a boyfriend but didn't even care that he blacked out in bed with his creepy ex. A...

In manga and manwha, basically only penetration counts as cheating.

Any sexual intent is cheating to me. But hey... they don't seem to think so.

I agree. However, if the person is unaware or/and raped. I would never consider that cheating. If something happened between Hajin and Jaehee, it would had be nonconsensual and I don’t view that cheating on Hajin’s part. But I do for Jaehee.

You're never fully aware when drunk that is true.
But being drunk isn't an excuse. Being drunk doesnt allow you to cheat and not face consequences. Being drunk with someone volontarily is being aware that there could be consequences. It's a risk you take by being drunk.

Please, so no one should drink with others in case they get accosted? First, maybe he felt he was broken up since he just found out his boyfriend has lied to him since day one. Second, cheating is making a decision to be involved with another person.. he didn't make that decision. He went for drinks because he was upset. He has a right to do that. What if he didn't drink, but simply fell asleep and was touched by someone, is that cheating in your world?

I had to reread my comment to you because I was seriously confused. I don’t say anything about being drunk. I never claimed it was an excuse. To be honest, drinking seriously impaires people ability to think and they make bad choices being drunk.
Lots of people considers drunken sex to be rape giving the circumstances. If someone was drinking an unknowingly spike drink and get drunk and someone raped them. I don’t think they cheated on their partner. No being drunk is not a complete excuse whether it is knowingly or not. It is the actions of the other and the circumstances.

Most of the time, people being drunk did not make that choice and will not make that choice.

My comment was more so on this. Hajin had rejected Jaehee many times, and even told him to go home. Jaehee should had learned as Hajin was getting drunk, Hajin was in love with someone else and had completely rejected him. If Jaehee did something, it would had been entirely his fault. Hajin would never consented. If something happened Hajin did not cheat. nonconsensual sex is not cheating. It is rape. You know, if you go back to the comments. Many readers had consider what happen in chapter 8-9 to be rape. Some even dropped this because of that. But there is a big difference in between chapter 42 and chapters 8-9. A few difference. Hajin was awake and not asleep. Hajin even though he put a distance inbetween him and Hangyum, and thinking he could be the one he went to school with. They had to work on the past. He still desired Hangyum and had that dream in chapter 4. He did regret it but he had other reasons which becomes clearer by chapter 40.

Since I have read 43-45. There will be consequences and more to come. I am not sure why I got a heated reply on drunk sex. But maybe I have vast knowledge of being drunk and what happens since I know someone who is an alcohol and drug therapist. They practice their lectures on me for their classes. It is the circumstances of being drunk that matters. And in the case of chapter 42, it is not cheating if something happened. But nothing happened. I am going to have to retranslated those lines but I think they are different from the official English translation. I don’t remember one night stand being said. I remember where calling Jaehee a bastard I think,,,,, it has been a few weeks since I looked at that chapter. The English translation has a different feeling from the Korean. It could be their localization/westernized bit. Or it could be me since I am only a beginner at Korean. I will ask someone better at Korean to look at that line.