After being prodded by a junior staff member about whether she intends to get married, Haruna, feeling ashamed of her single status, accidentally blurts out that she has a fiance. She tries to take her own words back, but the conversation goes out of control, and Haruna finds it harder and harder to tell the truth. Then, the CEO Soichi offers Haruna a fixed-term marriage contract! Thus begins the marriage contract (sex- included) between the devilish, sadistic CEO and the office lady who can't be honest with her own feelings! 見栄っ張りなOL・晴奈は寿退社をする後輩にナメられまいと、つい「婚約者がいる」と嘘をついてしまう。 取り消そうとするけれど、どんどん本当のことを言いだしづらい雰囲気に…！ そんな晴奈に、天敵の社長・総一が1年間の契約結婚を持ち掛けてきて!?