I had to look back and see what you mean but omg I really hope he did meet someone else and is happy cause they'll be a really good and realistic ending I find
Yea his part of the chapter just look like he was being thankful to Jooin for this new life, it didn't feel like he was planning go back. But I could be wrong. It's just Yahwi looks like the one who would be able move on more quickly than the other two, as he doesn't have many scars in the relationship nor was he basing all his love on Jooin. So I feel like this ending is perfect for him.
I’m assuming he became friends with the blonde twins and started a company with them. He probably became friends with their family too.
Random asf but like, is Yahwi in a new relationship lol he looks like he's sitting way to comfortable next to the dude in the picture, with his legs crossed as if he's sitting on top of him. Yahwi seems to happy where he at right now and thankful to Jooin for his new life.