I found the similar comment, hehe don't try to put any logic in yaoi
This one has no logic whatsoever om't tire yourself
Comment from the future here.
1. It wasn't a "measly punch". He punched his face in and knocked to the ground. That kind of force in real life would have anyone incapacitated for a length of time. The manga doesn't really do it justice. Real people don't just bounce up after getting punched like that unless they have went through some serious training.
2. The uncle let them go most likely because he doesn't want to get a shitty reputation as a incestuous raping piece of shit. If the uncle tried to keep his nephew , the heir to the family's estate, there then he would have probably sought some form of retaliation. Or at least that is how I see it. He could have also gone to the authorities too. Either way, his name would get dragged though the mud. Also he probably deemed it not worth it at that point. Still dealing with the after-effects of that punch.
..........okay if the guy drugged him and intended to rape him and all why did a measly punch keep him out of the room? honestly I find that odd and then he just lets him go? Honestly all the emotions in this story are confusing. its odd how he slept with a person he apparently wanted to kill....well besides the messed up stuff I was happy to see him smile in the end.