Lee Shin becomes your stepbrother when your mother and his father get married.

Lee Shin is a famous person in his school, even other schools know him. he is famous for being extremely handsome, good at fighting and because he changes girlfriends like he changes clothes

As no one knows, the person he loves is you, his step sister is 1 year younger than him.

Although in front of you he is always grumpy but he always climbs the window into your room when you sleep.