Kim Myungsoo is a highschool playboy who fall in love with his own stepsister, Park Jiyeon.

Park Jiyeon is a transfer student from California, she has a boyfriend who love her so much and will do anything to make her happy.

Park Chanyeol is Myungsoo's bestfriend who turn to be his rival because he dates Jiyeon.

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Anything will be revealed soon as the story goes.