Revivre (2015)

Native Title: ??
Also Known As: Thorn , Ttalgiuyu , Strawberry Milk , Gasi , Gashi , ????
Screenwriter: Lee Sung Min
Director: Kim Tae Kyun
Genres: Thriller, Psychological, Romance, Melodrama
Tags: Nudity, Taboo, Student-Teacher Relationship, Sexual Content, Student Female Lead, School Setting, Married Male Lead, Teenager Female Lead, Adult-Minor Relationship, Age Gap [Drama Life]

A man who recently lost his wife to cancer fantasizes about a young woman at work.

While vacationing with his wife, a writer begins following an older man and a younger woman who are guests at the resort hotel where he stays.

Both are about older men being attracted to younger women, about being in a very conflicting position- being stuck between his ailing wife and the new young employee at work in Revivre, while in A muse, it's between his assistant writer and a high school girl. Although, I personally liked Revivre more with its approach, I highly recommend watching both!