Do S Shachou to Kousai 0-nichikon: Keiyaku ni Sex wa Fukumaremasu!?

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!

(Source: Pocket Comics)