The drama begins when Yoon Ji-ho is displaced from her apartment after her brother marries. Due to a mutual misunderstanding over gender, she leases a room from software engineer Nam Se-hee. Upon discovering the truth, they formalize a two-year contract marriage: Ji-ho secures affordable housing without a deposit, while Se-hee gains a reliable tenant and recycling partner to help finance his thirty-year mortgage while appeasing his conservative parents.
As domestic cohabitation softens their defenses, Ji-ho uncovers the root of Se-hee's emotional paralysis. Twelve years earlier, his father forced him to separate from his pregnant girlfriend, Ko Jeong-min; following a miscarriage and their painful breakup, Se-hee locked away his feelings and vowed never to love again. Complications peak when Jeong-min reappears as a successful CEO offering Ji-ho a writing contract.
Recognizing that their transactional contract prevents Se-hee from acknowledging his true feelings and compromises her own agency, Ji-ho terminates the contract and leaves. This separation forces Se-hee to confront his grief and voice his love. In the finale, Ji-ho returns, and the two reconcile as true equals, establishing a renewably defined partnership built on voluntary choice, emotional transparency, and mutual respect.