Classi9

After the death of her father, Ren Taki travels to Vienna to fulfill a promise she made to him: attend the Melite Conservatory of Music. While traveling there, she meets the flirtatious musical wunderkind Wolfgang Amadeus Mozart, who is surprised to hear her plan to enroll at Melite.

As it so happens, Melite is an all-boys school! After talking with the headmaster, Ren enters the school as a student under the male alias "Rentarou." Sworn to secrecy, Mozart is assigned as her roommate. In this new place, Ren meets eccentric classmates such as Johann Sebastian Bach and Pyotr Ilyich Tchaikovsky; but since they live in the same dormitory, keeping her secret from them is a difficult and never-ending task.

With Mozart's help, she hides her gender while making every effort to remain in the prestigious school. Surrounded by peers of unimaginable talent, Ren strives to match their skill and compose resonating musical pieces.