Aoi Housen (蓬仙あおい, Hōsen Aoi); Seiyū: Houko Kuwashima; VA: Alexandra Carter
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.Citation needed 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.
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.
It is soon apparent that Aoi harbours feelings for both the Aiba brothers. However, building on her relationships with the boys was impeded. By the time Aoi realized what her feelings were, Kouji was pursuing a relationship with his own crush, Fina S. Shinozaki, and Yuki's attitude made it impossible for any save the most foolish or most persistent to get close to him. By the end of the series, all relationships and emotions are resolved, and Kouji and Aoi return to the Ryvius as an official couple.