The Second Mother (2015)

 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. In the end, Hee-ran and Se-min break up.