10musume 121314 01 — Azusa Sasaki

: A character named Azusa Sasaki also appears in the Sound! Euphonium franchise, where she plays the trombone for Rikka High School. Azusa Sasaki - IMDb

This indicates the specific internet distribution label or production studio responsible for creating the piece. These labels often operate under larger corporate parents but maintain distinct branding. 10musume 121314 01 azusa sasaki