Blue Orchestra is based on the manga by Makoto Akui, which began in 2017 and has ten tankoubon volumes as of April 2022. The series is serialized in Shogakukan’s Ura Sunday magazine and Manga One app.

Indonesian publishing company Elex Media describes the plot as: 

In the fall of his third and final year of middle school, Hajime Aono, a violin prodigy, stopped playing violin for his own personal reasons. But it was also that year when he got to know a girl who told him about a high school with a prestigious school orchestra. Suddenly, the gears in the clock of Aono’s life began to turn again. This is the story of a youth drama that brings forth the harmony between music and the heart!

Source: @nhk_animeworld