Aoki has a short spiky black hair with a little bangs on his forehead. He also has a goatee. He wears a simple black suit with blue tie. He also wears black leather shoes. He sometimes wear a pair of black gloves.  He also carries a gun as his weapon.
Aoki always shows a calm expression.
It is unknown whether Aoki has an ability or not, however he is skilled in martial arts.  However, he is swift with handling a gun. This is seen where Dazai pointed a gun at Ango and he immediately pointed his handgun at Dazai with considerable skill. 
Aoki is seen with Ango when Dazi made meet up with thim to negotiate something. . Later, he is seen at the library waiting for Tanizaki and Atsushi. He then guides them to a secret passage which reveals a room housing the Night Crow. 
After Taneda suffered from great injuries, which led him to being hospitalized. Aoki with Ango and Murakoso visit him at the hospital. Aoki is seen worried aout Taneda. After Ango decides to leave, Aoki asked if he don't want to say close by the chief's side to which ANgo replies that they are not that close. Aoki and Murakoso are left at the hospital guarding Taneda.
- The character is the protagonist in one of Ango Sakaguchi's novels, "Blizzard Story (吹雪物語)".