Who are those people at the end?

One of them is Jaehwan's old sunbae from college. The one he had a crush on but didn't return his feelings.

lmao this manga took like a long hiatus and I havent reread this yet... who's Jaehwan?

The blonde part timer

Jaehwan is the other worker Mr. Yoon (jinwon) hired. He is currently in a relationship with Byul's younger brother Dongho.