Robot maker, Kronos Heaven, finally develops "Night Tenjo", the perfect male humanoid programmed to be devoted and completely loyal to his lover. The company chooses temp worker Izawa Riko to take part in a 5-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 Asamoto Soshi, a distinguished young executive at her company who has feelings for her.