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. Neither Kouji nor Yuki appreciate her concerns; nor, it appears, do their respective girlfriends, Fina and Cullen. The manga adaptation of Infinite Ryvius is taken from Aoi's viewpoint, in contrast to the anime, which was mostly seen through Kouji's eyes.