I feel a bit dumb.. can someone explain to me:

I don't know about any cheating but the day Chun Sam confessed to him he slept with some other guy right after.

yes he did

whaaaa ╥﹏╥ no chun sam is way to good for cheating

Technically, he didn't really cheat on Chun Sam since they're not in a relationship yet when that happened. It's more like Min Gyum haven't yet developed any feelings for Chun Sam at that particular point of the story. It was only after all that that Min Gyum started seeing Chun Sam as a potential lover. But before that they weren't so... he didn't really cheat. But yeah Chun Sam's a good guy ╮(￣▽￣)╭

oooooohhhhhhh thanks! (=・ω・=)