So I think the club scene shows clearly that he is quite maipulative, that goes beyond just flirting and being clear about his intentions. I onced described it in comment:
" Jae Eon knows what's up. He took her clubbing - crowded place, full of drunk strangers, where you can barely rely on your senses and there is no place of peace where you can just chill and have a moment to collect your thoughts. She will be drawn to him more, to rely on him, since he is the familiarity in the chaotic place. Damn. He took her to a place that will make her anxious, nervous, maybe irritated and then probably offer himself as a comfort, and she will not say no lol " and that's exactly what happened. He saw her being EXTREMELY uncomfortable in that club, he smiled seeing her in distress (if someone smiling seing someone else being uncomfortable is not a red flag, I don't know what would be 🤣) and then used that to make her focus on him and gave her sense of stability, while at the same time being the one who brought her to the chaotic place in the first place (and there is no way he did not know clubs are not her thing, it's obvious). It's the same as guys getting a girl drunk knowing she will struggle with saying no to the drinks, and then acting like a hero taking care of them.
Another thing is: he can hook up with other girls, be close to other girls and have many female "friends" while at the same time getting possessive over her when she gets close to other guys. There is no balance here. Either they are friends with benefits that can hook up with other people, or they are in a monogamous relationship. But he has different standards towards himself than towards her. That gives her mix signals.