Pretty Young Sister 5.

Yeon-joo feels good about Min-soo who found his cellphone, saying that it is fate. Although they are dating, she is disappointed in Min-soo. While kissing at Min-soo's house, roommate Jae-kyeong catches them. Yeon-joo is hurt when Min-soo had to hide her from Jae-kyeong. Jae-kyeong comforts Yeon-joo and begins a new fate. And the truth that Jae-kyeong is the person who found the cellphone has been revealed...