I feel like everyone in this story are not wrong nor either right. Taejoo was of course has been suffering a lot but then youngwoo came to him to comfort. And when Yoon came back to life, well of course Yoon had to suffer to which makes youngwoo to feel insecure. (I would feel insecure if my bf was acting like that) youngwoo truly love Taejoo and Taejoo and Yoon truly loved each other. My thought, Taejoo was mistaken about loving youngwoo cuz he was there in taejoo's most difficult time. Youngwoo suffer a lot when Yoon came and Yoon suffer when he saw the two of them together. Just my opinion but no one in this comic is wrong