Fraternal twins Si-yeon and Si-ah couldn't be more different; one never wants to leave her room while the other is a big K-pop star.

A new semester begins, but Si-yeon is already counting down the days to the end; Si-ah shoots a commercial with her not-so-collaborative partner.

To reverse the magical mishap, Si-yeon goes back to visit the tarot card reader with Si-ah, but bad news awaits them.

On the first day of living each other's lives, Si-ah runs into a group of schoolmates and Si-yeon messes up on stage.

Si-ah's singing ability tops the list of search keywords on the internet, but she's not thrilled about it; Si-ah gets a surprising text message.

Gyo-seok and his gang keep testing Si-ah's patience; Si-yeon and Hae-seong secretly meet up at the rooftop, but someone is watching them.