Major spoilers!!!
I say frustrating because in some chapters, you really can't tell what he's thinking so every move he does is sus
As for the chasing arc, it's kinda a long story but Dohyun was actually hired by MC's mom to monitor him. This gets found out by MC and they broke up because MC felt betrayed and Dohyun really regrets keeping it a secret for too long (man was going through it in those chapters lol it was all his pov), so he proposes that he's gonna court and prove that what he's really feeling for MC is genuine until Wooyeon forgives him

Dohyun only seems nonchalant on the outside lol that man is just good at being all mature and keeping secrets bc of his past (which was a bit surprising). He does like and have fallen for MC genuinely
He IS a bit frustrating in the later chapters but the chasing arc was quite satisfying personally and his POV was really nice to read