Bruh it's completely different from what the parents did. The mom left him all alone with an abusive father and she never came back for him. All hyesung is doing is trying to cope with his trauma. Sometimes people need to be alone in order to heal. And hyesung isnt leaving him alone with no one to take care of him. He obviously knows that there are others who can care for him. He should be allowed to at least spend some time alone.
The first time he left Byul he actually didn’t know if anyone was there to take care of him. He is just starting to follow the same path and he obviously needs to go to actual therapy rather than running away since it has shown it doesn’t really help him have any growth.
Believe me I hate the dad and even the mom character but I don’t want to see him continue to use these coping mechanisms because they aren’t healthy he needs to get professional help from a therapist.
Yes I agree that he should get professional help but right now hyesung just wants to be alone. Until he himself decides to seek help he should be allowed to be alone, the only reason anyone should intervene and force him to get help is if he tries to harm himself. And like I said before the mom left and NEVER came back for him. It's different from when hyesung left bull because he still came back. And I'm pretty sure he did know that byul was being taken care of because heeso told him. And Hyesung did go and visit byul secretly to make sure he was okay.
So Hyesung is upset and traumatized because his dad was absent emotionally as well as abusive and his mom just was not there for him and to cope he goes and be emotionally absent to his child as well as not being there for him. Like he needs to realize he is doing what his parents did minus the physical abuse