From Syuura:

During a field trip to the imperial capital, Tokyo, Kaga Nanao overhears the beautiful melody of a violin and immediately becomes captivated by it. In order to meet the mystery violinist, Nanao learns the violin and defies her father's wishes by attending the Marianne Music Academy for girls in Tokyo. Upon arriving at the school, Nanao comes across her mystery violinist who turns out to be Sagami Takenomaru, the violin prodigy and adopted son of the famous violinist, Sagami Chougo-sensei. However, Takenomaru isn't just a regular person, he's determined to complete a mission and fulfill a contract...

Note: "Naki Shoujo no Tame no Pavane" means "Pavane for a Dead Girl" and is a wordplay on the Japanese translation of a solo piano piece, written by French composer Maurice Ravel in 1899, called "Pavane pour une infante défunte" - Naki Ōjo no Tame no Pavane or Pavane for a Dead Princess.