what an asshole
The uke thought he was engaged/married because of the ring but actually it was only for show. The seme wasn't married and actually came to the reunion wearing that cause he had plans of proposing to him there. Actually the seme wanted to straight off confess his feelings after graduation but the uke just vanished in thin air after the ceremony and there's a scene where the young seme stood all alone infront of their classroom door for the last time with a bouquet in his hand. However, after all this years, he wanted to have another chance. And when the uke fell asleep after sex, the seme put the ring on the uke's ring finger (as in propose). But the uke had always been insecure even tho he had feelings for the seme but now, ofc he had no point in trying to have a relationship with him when the seme's already married (in uke's point of view). So he just treated the incident as an one night stand and left as soon as possible but then reaching the train station, he suddenly noticed the seme's ring on his finger. He finally got what it meant and ran back where the seme was also searching all over for him in the fear he has lost his love again and forever.
I hope this magazine guy won't find out about their relationships otherwise its going to be a huge scandal and I don't want to see haesoo heartbroken┗( T﹏T )┛