The Beauty Inside — Ending Explained

I could not find a detailed plot summary of the second half, so this section is limited to what the sources confirm. Woo-jin's changes begin at eighteen, and he falls in love with Yi-soo and tells her about his condition. The relationship strains her. Woo-jin ends it to improve her mental health, and she later speaks to a therapist about the strain of loving a changing face. The film then closes on her recognising him again in another body, which a Letterboxd reviewer describes as a cute final scene featuring Woo-jin in the form of a woman played by Chun Woo-hee. The central message is that Yi-soo has learned to recognise Woo-jin in whatever form he takes.

The shifting faces can be read as a metaphor for any long relationship, in which a partner changes with age, illness and mood. A second reading is a metaphor for mental illness or disability, where the loved one 'isn't themselves' on some days. A third reading, raised by critics, is a feminist one: the story is as much about Yi-soo's emotional labor as about Woo-jin's condition. Others note that the premise is safely treated, and that the film avoids exploring gender fluidity or race in depth.