|Instrument||Viola (previously Violin)|
|School||Seiso Academy Regular Department|
|Grade||Second year class 2|
|Physical and Vital Statistics|
|Manga||Volume 11 Chapter 47|
|Anime||Season 2 Episode 1|
Aoi Kaji is one of the new characters that appears in the second game and was introduced later in the chapter 47 of the manga. He's a new student in the General Education department, who transfers to the academy and is placed into Kahoko's class.
Aoi is extremely smart and athletic, though has a rebellious streak of his own. He also admits that he doesn't have confidence in his own performances since he lacked training, but he has very sharp hearing and can easily spot flaws in others' performances. He is also very fast in tuning his instruments.
He previously played the violin but dropped it and now plays the viola because of an incident in the past. It was shown that when Kaji was still a child, he attended the same class with Tsukimori, Ousaki, and Etō. However on the day of the recital, he backed out after hearing Len's music. It was inferiority that broke down his confidence.
His grandfather owns a hospital and his father is a politician. His grandfather hopes that he will major in medicine, so that he can someday take over the position as head of the hospital.
His parents were alumni of Seiso, which was indirectly revealed when Aoi asked his father to tell him more about the school.
- His hobbies are playing tennis and reading.