
WARNING: S P O I L E R !!! A L E R T !!!
ohh okay,,, i might be wrong but as far as i can remember he's Eunki's sunbae from the university, the sunbae is the other sunbae's (from the guitar club that Eunki were in, and the girl she likes... before,) boyfriend. He holds a grudge against Eunki coz his gf had a "relationship" with Eunki before, he's also the one who spread rumors about Eunki dating his gf but in fact, it is his gf that wants to be with Eunki and didn't tell that she's in a relationship. But to not ruin his (the sunbae) reputation and his gf's reputation he made Eunki the bad guy in the story. Sorry if I didn't explain it thoroughly, I might also be wrong since the plot from the original "Fools" kinda changed.
It's THAT dude right? Don't stir up drama will 'ya?