Responses
It was already brought in the story that he did. Whenever he has special feelings for someone, supposedly his first relationship that lasted so long with Minji, he kept her stuff and did not really throw them away. So I believe he did. Also in the recent chapters Yeonduk said he never thought he would ever hear the soft and gentle voice that Skyer uses when speaking to his significant other beingdirected towards him. And you see a flashback of Skyler on the phone presumably speaking with Minji his first serious and long term love interest.
so
yeonduk thought minji, skylers ex, was skylers first love but skyler says that yeonduk is/was his first love. i guess what i really want to know, is even if minji wasn't his first love that doesnt mean he didnt like minji at some point right? idk, someone help me not feel so petty. did he have any feelings at all for his ex?