She Would Never Know(2021)

Original title: 선배, 그 립스틱 바르지 마요

Yoon Song Ah works as a marketer for a cosmetics brand. She enjoys her job and dreams of launching her own brand someday. Chae Hyun Seung is a fellow marketer who becomes attracted to Yoon Song Ah. He tries to develop a romantic relationship but Yoon Song Ah rebuffs his advances, not wishing to date younger men.