Ritsuko Akine

Akine is a 15-year old girl with wispy chest-length auburn hair that is typically styled with two mini pigtails, royal blue eyes, a slim body and she has a great physical stamina.

She is often seen wearing her school uniform which consists of a red, blue, and white bowtie, white button up shirt with a blue blazer adorned with the Umimaku High School symbol, and blue skirt.

(Source: Ao no Orchestra Wiki)