I'm pretty sure that's the guy her ex best friend (with the blonde hair) used to like, the one that they had a falling out about cuz her friend thought she was seeing him behind her back, which lead to the whole scandal that Dawoon went through
Honestly this webtoon was so good to the point where I wasn’t focused on the smut scenes LOL. usually when I’m reading yaoi im like yes dicks ლ(´ڡ`ლ) but when I read this I was like wow this is I am emotionally nutting this was so good.
I still don’t forgive the alpha seme for all he’s done ヾ(❀╹◡╹)ノ~