To put it simply, Youngjae is Jaebeom’s best friend Mark’s ex-boyfriend from college. That’s why it’s technically wrong on so many levels that Jaebeom and Youngjae have had a crush of each other since their college days, since as far back as when Youngjae was still dating Mark. After college, Jaebeom moved away, but now he is back in Seoul, he is single, Youngjae is also single, they still like each other, and well.... you can't choose who you love. A lot of guilt and internal conflict ensues