This scene is like being lovers and having been together for many years. It's a very natural picture when they're together, not uncomfortable being themselves, and when they stop being together it makes each other feel a lot more confident.
He felt that to minji (awkward) because all minji do is being lovey dovey to get his attention more like a she's seducing him more than getting to know each other ..unlike Hyeseon that there's a boundaries from getting to know and being friendly with both that's why he's more comfortable with Hyeseon that's it
Towards the end he had a blck hairband on one of his wrist and I wondered who it belonged to but this clip reminds of there is big possibility the hairband ended up in his wrist here❤x