Cyan Hijirikawa is a shy high school girl who loves music and wants to become part of band but is too shy to ask to join one. One night, she is suddenly sucked inside a rhythm game on her phone into a musical world known as Tokyo Midi City, being intercepted a talking pink guitar midflight. When she regains her senses, Cyan finds herself in a cat-like form, witnessing a performance by the band Trichronika. Just then, a mysterious monster appears, attempting to drain the power from the Melodisian Stones in Trichronika's hearts in order to turn them dark. Spurred on by her guitar, named Strawberry Heart, Cyan manages to defeat the monster with a guitar jam. Shortly afterwards, as Cyan now finds herself in a catgirl form, she is scouted by Maple Arisugawa, the CEO of the Branded Rocking Records record label, to become a member of his band Plasmagica, and is introduced to fellow members Chuchu, Retoree, and Moa.