Irreplaceable Kiss Scene

Is there a top actor who turns into a 7- year-old child just by kissing?! Due to an accident, stunt double Kang-som must take responsibility for the actor who has transformed into a child because of her. A life of bickering with a prickly and sensitive superstar! While they worry about being found out, an opportunity for Kang-som to become a popular actor arises...?!