Seongsilhan Chaemuja?

I'll come borrow again next week♥ Chae-Seong, who runs a loan shark business, unfortunately got tangled up with a creepy guy named Yu-On. He's a sucker customer who pays back without batting an eye even when I pile interest on top of interest, but his sinister gaze is unbearable. This won't do. I need to teach this bastard a lesson, don't I? (Source: MrBlue, translated) *Note: Includes one extra chapter.*