So the story goes like this

In the past they both loved each other, but as y’all know long time ago falling in love with the same gender wasn’t accepting mainly because men couldn’t get pregnan... that’s why they didn’t end up together, but when hosik was dyeing in bed he told sungyeon that he loved him.. sungyeon promised that in their next lifetime he will never let him go and that no matter what others do or say he will stay with him. That’s why you can see in the beginning sungyeon falling in love with hosik the first time he met him and the way he kept on staying next to him.. you could say in a way he doesn’t remember his past promise but that doesn’t mean that he won’t fulfill it because he loved hosik. And the way it ended with hosik standing next to the cherry blossom means that their love never died out and their souls never forgot, meaning that they are now finally able to be together and have a family (๑•ㅂ•)و✧(づ￣ ³￣)づ