Living with the couple is Hyeon-seok's younger brother, Hyeon-soo (played by Min Do-yoon). The two brothers often engage in casual, "useless talk" about the new live-in housekeeper who has moved into their home. This housekeeper is Se-hee (played by Kim Min-jeong). She is described as having a certain charm that becomes the subject of the brothers' speculative conversations.
Housekeeper - My Wife's Friend belongs to a specific sub-genre of late-night South Korean cinema (often rated 19+) that utilizes melodrama to explore taboo relationship dynamics. Unlike traditional Hollywood thrillers that rely on physical danger, these films emphasize emotional vulnerability, the shifting of leverage within a household, and the contrast between public success (Mi-jeong's corporate life) and private dysfunction.
Min-woo develops an increasingly intimate relationship with Mika.