At 16 years of age and a childhood friend to Kouji, Aoi has known the Aiba brothers longer than anyone outside the Aiba family and acts alternately as an older sister and a mother figure to both boys, often going out of her way to check up on them. A flight attendant trainee aboard the Liebe Delta, Aoi often sticks her nose into Kouji's business, but only because he is weak and spineless and not because she has any special feelings for him. Neither Kouji nor Yuki appreciate her concerns; nor, it appears, do their respective girlfriends, Fina and Cullen. Outside of her dealings with the Aibas, Aoi is fast friends with her fellow flight attendant Kozue Izumi. She is also friends with classmate Reiko Ichikawa, though this relationship is not as close as the one with Kozue. All three flight attendant students roomed together on the Ryvius - although eventually Aoi is the only one left occupying that space.