Kwon Yuri, a normal girl who had a little stepsister named Jung Soo Jung, or Krystal. Yuri is dating with Kai, and when Kai and Krystal met, Krystal fell in love with him. She keep telling lies about her sister because she wanted Kai to break up with Yuri. When Krystal was dating Kai, she met Jessica Jung, Kai's closest friend. Krystal realized that she wasnt actually Yuri's sister, but Jessica's. What happen?