Choi Sooyoung and Choi Siwon are bestfriend since their are 10 years old. Siwon went to L.A. for his job. After a few years, he came back with her girlfriend Jessica Jung. Later, Siwon needs to go back to L.A. for another year and he asked Sooyoung to take care of Jessica when he is not here.

What will happen if Sooyoung fall in love with Jessica? Will Jessica loves her back or just use her like a substitute during Siwon absence?