What are these self-sabotage. Clam-blocking at its finest, at this point only Hayoon deserves Taesoo.
First love is a bitch. It’s hard to let go when the relationship never really had a definitive ending. I believe that’s what Taesoo is feeling. Realistically, after spending all those years trying to find her, he probably should have fallen out of love with her by now. At that point, he may not even be looking for Mia because he still wants to be with her, but because he needs an answer and a proper ending.
He even said himself that he has simply grown tired. Realistically, I think he should still love his Sunbae, but what he wants from Mia now is closure—so he can finally put the past behind him and move forward.