Well
....
From what I can gather (I don't understand a word of Korean) it seems the red head actually like Teasing. He comes on to him eventually and quite immaturely... And then is rejected obviously.... So I think he tries resorting to some sort of blackmail... Alas, Taesumg is a smart cookie and turns it around at him.
I won't spoil it too much, but let's say he makes the red head look like he's in a very compromising position that could potentially get him fired at work. I could be all wrong, extrapolating from seeing the panels workout being able to read
Damnn, it is time to beat that trash then
Gimme more spoiler~~~