Robot maker, Kronos Heaven, finally develops "Night Tenjō", the perfect male humanoid programmed to be devoted and completely loyal to his lover. The company chooses temp worker Riko Izawa to take part in a five-day free trial. At first, Riko only sees Night as a household appliance. But when she finds out how deep Night's devotion to herself is, Riko finds herself falling in love with him. Joining the love triangle is Sōshi Asamoto, a distinguished young executive at her company who has feelings for her.