Kono Oto Tomare!

In the story, Takezou is the last remaining member of the koto club, a club dedicated to the traditional Japanese string instrument. If he doesn't find new members, the koto club will be terminated. One day, Takezou is alone in the club room when a student barges in and demands to join. The student is delinquent Chika Kudou, a guy who even scares delinquent upperclassmen at other schools.

(Source: Anime News Network)