Hee Ran was a karaoke mistress when she first met Se Min through a marriage consultant company. He suggests they should have a contract marriage; she would get paid every month for being his wife and Se Gyu's mother. Hee Ran thinks this is a good deal but unlike her thoughts, being married is boring. Se Min only needs her at night and Se Gyu has a crush on Hee Ran who is like an older sister but hides it by being nasty. One day, Hee Ran meets Se Min's friend Tae Yeong and falls for him.