The “idol” sisters, SNSD’s Jessica and f(x)’s Krystal, are to sing a song for the sound track of SBS’s new drama series To the Beautiful You. Jessica and Kystal are blood-related sisters, and it is first time for them to perform a duet with the song “Butterfly,” a song for the sound track of the series. “Butterfly” will be playing as a theme song for romantic scenes because it has lyrics that express one’s first love and sweet melody. Another singer J-Min, who belongs in SM Entertainment as the two sisters, will be singing “Stand Up,” the theme song. There is an emphasis on strong guitar sound and drum beat in the music. Another duet song by SNSD’s Sunny and f(x)’s Luna will also be included and soon to be released, building up fans’ expectations. You can first check out “Butterfly” and “Stand Up” at noon of August 15 on various online music websites.