Aoi has deep blue eyes that fade to a lighter blue at the bottom, along with white pupils, straight black hair with a parted fringe, and twintails. She wears two blue butterfly clips to keep her twintails in place.
As Aoi is a Demon Slayer, she wears the standard uniform with the addition of a white nurse dress on top of it. Her uniform is tinted slightly blue. She is often seen with a frown.
As she trained Tanjiro Kamado, Zenitsu Agatsuma, and Inosuke Hashibira, Aoi is very tough on them, often pushing them to their limits. She has a firm personality, unlike her colleagues at the Butterfly Mansion.
Aoi's personality is somewhat similar to that of the young Shinobu Kocho, volatile and open. She often appears angry, generally displaying how she feels very clearly. However, she does occasionally express more tender emotions such as declaring her enjoyment of the time spent with the trio when they were at the Mansion, looking openly surprised at Tanjiro's reassurance towards her, and bursting into tears when discussing Inosuke's serious injuries.
Despite her somewhat gruff demeanor, she is internally kind and caring, doing her best to help the hunters that come to the Mansion.
Aoi managed to survive the Final Selection, though she claims that it was through pure luck. She was too afraid to go in to battle despite passing the Final Selection and as a result, decided to work at the Butterfly Mansion instead. She seems to undervalue her own work, claiming that she isn't doing much compared to full fledged hunters.
Although she cannot fight, she is well versed in medical knowledge and was presumably taught by Shinobu. She helps with the upkeep of the Mansion and cares for injured hunters.
Aoi first meets Tanjiro when she discovers him and the Kakushi talking to Kanao Tsuyuri in the garden. She brings them inside to the recovery beds, displaying clear frustration at the injured Zenitsu's constant wailing. She provides care for the trio throughout their stay.
During the training portion of their recovery, she explains the general ways they will be trained, including massage, reflex training, and tag games. Aoi and Kanao both play the reflex and tag games. Aoi is quickly beaten by Zenitsu, who refuses to splash the medicinal water on her. She is still displeased with him, as she had heard his rant about how wonderful it would be to train with girls, since he gets to touch them. He also beats her in tag, but she punches him when he gets too touchy.
Aoi is also beaten by Inosuke in the games, and later by Tanjiro. She becomes annoyed when Inosuke and Zenitsu stop coming to training.
When the trio depart, she tells Tanjiro that she enjoyed sharing her time with him, and wishes him good luck. Tanjiro responds by thanking her for taking care of him, but she deflects this by saying it wasn't much since she can't fight like others. Tanjiro tells her that being unable to fight has nothing to do with it and that since she helped him, he'll carry her feelings into battle as well. Aoi seems surprised by this response, but not unhappy with it.
Aoi once again helps care for the injuries of the trio following their fight on the train.
Aoi and Naho Takada are both picked up by Tengen Uzui, who wants them to help infiltrate the Red Light District. Kanao Tsuyuri attempts to stop the Hashira from taking the two girls away, but having trouble with her own lack of resolve, she does not say anything to stop him. Tanjiro interrupts the commotion and asks Tengen to release the girls, to which Tengen responds that he needed a female Demon Slayer for his mission and had planned on taking Aoi and Naho. When one of the younger girls explains that Naho was not a Demon Slayer, Tengen drops her and instead plans on only bringing Aoi. Aoi appears distressed and upset when Tengen commented that even if she wasn't useful, she was still a member of the corps. Tanjiro, Inosuke, and Zenitsu eventually volunteer to go in Aoi's place, releasing her.
Abilities and Powers
- Medical knowledge: After training under Shinobu Kocho, Aoi is able to concoct most of the more simple medicines.
- Above Average Strength: While Aoi is weaker than most of her fellow Demon Slayers, she is stronger than the average person, having gone through training under Shinobu and passing the Final Selection.
Aoi and Tanjiro seem to have formed a friendship. Tanjiro respects Aoi for her help and care while he, Inosuke, and Zenitsu resided at the Mansion. He also thanks her for her work and assistance, which she seems to appreciate. He intervenes for her when she was being kidnapped by Tengen, and defends her when Tengen says she isn't useful by saying that everyone has their own circumstances. When Tanjiro leaves the Butterfly Mansion, Aoi says she enjoyed their time together.
How close they are is somewhat uncertain, but the two get along and seem to have a somewhat sisterly relationship. Kanao attempts to stop Tengen from taking Aoi with him at a time when it was highly unusual for Kanao to make her own decisions or go against her orders. As seen in the novel, Aoi previously thought of Kanao as difficult to deal with, since she never showed her own emotions. She also felt inferior to Kanao, since Kanao could fight demons and Aoi could not. However, once Kanao starts to open up and make her own decisions, Aoi and her begin to grow closer.
Shinobu is Aoi's mentor in the field of medicine and likely oversaw some or all of her demon hunter training as well. Aoi thinks highly of Shinobu, like all the other butterfly girls. Shinobu cares for Aoi and feels sympathy for how her family was killed by demons. She also seems to feel some anger on Aoi's behalf, remarking that none of the butterfly girl's families would have been killed if it weren't for Demons during her fight with Doma.
They met each other, for the first time, at the Butterfly Mansion. At the beginning, he struggles to beat Aoi in all of the tasks due to not having a strong will. Later on, he is finally able to adapt and beat her. In comparison with Zenitsu and Tanjiro, he was more harsh against her. He was one of the slayers who volunteer in Aoi's place to go to the Entertainment District in a mission with Tengen. After the fight against Upper Moon 6, he's carried one more time to the Butterfly Mansion. Aoi is visibly sad about Inosuke's terrible condition, since he had poison through his body and she thought it was too late to stop the bleeding. Her tears were quickly dispelled however, as he drops off the ceiling. She starts to see him a as pain and start to argue with Inosuke again. At the Butterfly Mansion, he goes out of Tanjiro's room and heads to the kitchen to get some food. He tries to steal food behind Aoi's back, but she notices him. She hands him over a rounded tray of food that is made only for Inosuke and tells him that he can eat how much and whenever he wants from that tray. After this gesture, Inosuke visibly starts to see her in a good light.
- Although never explicitly stated, it is heavily implied that Aoba Hashibira is the great-grand child of Inosuke and Aoi. This is for a number of reasons, the most prominent of these being that:
- Aoba shares the romaji spelling of the first part of his name with Aoi (however, the "ao" in "Aoi" and the "ao" in "Aoba" are written using different characters). Given that Sumihiko Kamado, Kanata Kamado, Toko Agatsuma, and Yoshiteru Agatsuma all share parts of their names with their ancestors, it is possible this is also the case for Aoba.
- Aoba works in the field of science, much like Shinobu did back in the Butterfly Mansion where Aoi lived.
- Aoba has jet black hair rather than hair that fades from black to blue like Inosuke's, the same as Aoi.
- (To Inosuke Hashibira) "If you're hungry, eat this. This plate is just for you, so eat from it whenever you want. But stop stealing food!"