Seohyun, Yoona, Yuri were just kids when they move to Seoul with their mother's brother Yunho and his wife when their parents were kill in a crash, the aunt didn’t like the girls much. When their uncle goes out of town for business, their cousin Sunhwa, Hyosung and Ji Eun would get into fight with them at times and most of the time the sisters would be punish for hitting their cousin. When Yongguk and Daehyun came home from their camping trip with their first cousin Zelo and Jongup they saw the three girls at the dinner table with their family, their mother would told her two boys not to get involve with them, as time goes by and they were all grown up and went to the same school but act like they didn’t know each other. It was their junior year when three boys Kai, Ray and Kangjun from other school enter their high school when Seohyun caught one of the three attention. When Daehyun learn about one of the new transfer liked Seohyun he gets in the way. The hate between Yoona and Sunhwa disappear within one night when Yoona save her cousin Sunhwa from her boyfriend, Yuri was ask to date Jong up to keep his old girlfriend away when she agreed, but she didn’t know that this fake relationship would turn to something she didn’t want. Hyosung try to keep her cousin Jongup away from Yuri but it wasn’t easy as she thought, when Ji Eun notice the change in her brother towards Seohyun she also try to kept her brother away from her.

Yuri Yoona Seohyun are the Kwon sisters.

Hyosung Ji Eun Sunhwa Yongguk Daehyun the Bang siblings.

Zelo Jongup are the Moon brothers.

Kai Ray Kangjun are the Kim brothers.