Sawa Mizuno is a first-year high school student who is quiet and doesn't stand out. At the high school she attends, a band called "Blue Burst" which is made up of four members is very popular! Seems like Sawa and the band members have nothing to do with each other. But in fact, one of them is Sawa's twin sibling! Afraid of repeating a year and because it conflicts with his work , he convinces Sawa to attend his make-up classes - that means she has to pretend to be his brother?