Won Da-mon is Yul-seo's toxic ex-boyfriend. He is a physically imposing man who thrives on power struggles and masochistic tendencies—he actively enjoys being struck or degraded by Yul-seo because he knows she genuinely hates him. As a regular customer at her night job, he forces her into a position where she cannot legally or professionally deny him service, forcing her to endure his presence. He is cruel, obsessive, and uses his financial status to keep her tethered to the past she tried to leave behind.