Someone please explain . Who is he jealous of???

its like this. the mc liked yuseong hyung but yuseong hyung like the section chief which they were together in the past when the mc in college. so back in the past the mc already decided to put an end between his unrequited love which he hopes yuseong hyung happy w the section chief. but it turns out , that in this present , the section chief which ex bf of yuseong hyung like the mc. so he felt like pathetic that someone hes jealous of in the past like him now.

Aah okay clear now thanks (⌒▽⌒)