You know I never thought about it like that... I think it was more ewons choice. It wasn't a good idea to get re-involved with his mom (which would have happened if he kept contact with sis) but of course he will miss them. It's for the best tho and he knows it because its are not worth risking his new happiness. Mookyul truly loves him and that's why he let him go to begin with
But even if he's involved with his sister, that doesn't mean he has to be friends with his mom. You have friends, but you're not friends with their moms too, right? I have plenty of friends who's parents I've never met. At work, it's better to not be involved with negative co-workers, but that doesn't mean you just don't go to work (if not a better example). Will he really be happy if he looks back and wishes. Mookyuk's "true love" is beyond love, it's complete obsession, need for possession, and control. He flips if the dude isn't at the office in 10 minutes. In a real relationship, you don't just completely control each other. Sometimes there's family or friends around, and that's okay. Insecurity and ocd isn't that attractive.
I thought he could see his sister once in a while, but maybe it had to be an all or nothing decision for him. He finally gave himself "fully" over to Mookyul. I still was a bit confused on how things ended with the old man and Mookyul. I do think their sexual relationship ended as he promised Elon, and the old man adopting him helped changed the dynamics of their relationship. part of why Mookyul set up that one guy was to clear the old man and make them even so he could break away from him. Love this manga so much. I wish it could have been made into an OVA.
I really didn't understand why the situation with the sister had to be an "all or nothing" situation. Surely he could still remain in contact with his sister, even if he couldn't live with them. He even refused when Nabin brought up calling him...come on, it's just a call.
...was how he didn't give his sister a clear answer. honestly, it's not healthy for mookyul to dominate his sole thought and action. I think it's okay for Ewon to still be friends with his sister in the future, even if he remains estranged from his mother. I hope he can rekindle the sibling relationship in the future when Nabin is more mature & understands things a bit more.