Furniture designer Park Gae-in (Son Ye-jin) is kind, impulsive, clumsy, and a complete slob in her personal habits. She lives in Sanggojae (meaning "a place for mutual love"), a modernized hanok (traditional Korean house) designed by her father, a famous and reclusive architecture professor (Kang Shin-il). Naive and trusting, she has been dating longtime boyfriend Han Chang-ryul (Kim Ji-seok) for years despite the fact that he takes her for granted. One day, without so much as a word of explanation, he breaks up with her and all but disappears. Then Gae-in is invited to the wedding of her good friend and roommate Kim In-hee (Wang Ji-hye) and is horrified to discover that the husband-to-be in none other than Chang-ryul; the two had been cheating on her for some time. When she finally comes face-to-face with them, the wedding ceremony breaks out into utter chaos. Gae-in is heartbroken, and determined to never take a chance on a man again.
Meanwhile, to keep his small firm afloat, architect Jeon Jin-ho (Lee Min-ho) is desperately trying to win a project bid for the Dam Art Center against Future Construction, the prestigious company owned and operated by Chang-ryul's father (Ahn Suk-hwan). In order to win the favor of the Dam Art Center director, and win the moneymaking bid, Jin-ho has to find a way to dig up more information about the art center director’s favorite building: Sanggojae, which has never even once been opened to the public,.
Knowing that Gae-in would never let a man (let alone a stranger) be her new roommate, the straitlaced (and straight) Jin-ho pretends to be gay to get access to the house — and all the information that he's sure is hidden within. At the same time, the DAC director (Ryoo Seung-ryong), who actually is gay, finds himself attracted to Jin-ho. Once they start living together, Jin-ho gradually embarks on a mission to make over the inveterate tomboy/slob, but in all the mayhem of the makeover and hiding his true orientation, the unexpected happens and the perfectionist architect begins to fall in love with Gae-in. What will happen when the man who’s pretending to be gay and the woman who thinks he’s gay develop feelings for each other?