
Wtf... Hyung and Subin are perfectly fine together... Hyunwoo is the eyesore who keeps bothering Subin

You could have just said that lol. But it's not "unhealthy" in anyway, it's normal for a person to have lingering feelings when moving on, specially if it's very recent. Not to mention he liked Hyunwoo for years. You don't just forget all that in one night. Expecting Subin to be COMPLETELY free of insecurities seems so unrealistic.

Besides, he just said that he's not gonna have dinner with him and he took the effort of reminding Hyunwoo that it's not right for them to stay together because all that happened. Subin is taking small steps but he's getting there, and I think you're expecting him to take a gigantic leap of commitment in just a few days.
Honestly, it would be best if they all end up alone. Neither couple is healthy