Airi Arcadia

Airi Arcadia (アイリ・アーカディア Airi Ākadia) is Lux Arcadia's younger sister and a student of the Royal Officer Academy. Like him, she is a survivor of the Old Arcadia Empire's Imperial Family, making her a former princess.

Appearance
Airi has shoulder-length light grey hair and grey eyes, similar to the rest of her family. She wears the Royal Officer Academy school uniform.

Personality
Airi has a very calm temperament, as shown when she didn't panic even when an Abyss attacked the Academy. She is critical of her brother, but at the same time is confident in his strength and worries when he overexerts himself. She becomes flustered when other people tease her about her relationship with Lux.

Background
As a child, Airi grew up in a harsh environment due to being a girl in the patriarchal Old Empire. She suffered from an unspecified illness that made her body frail. Lux would always treat her and their mother kindly, which confused Airi since it resulted in Lux being looked down on by the rest of the royal family.

One day, Wade Roadbelt (Airi and Lux's maternal grandfather) criticised the misgovernment of the Old Empire. This caused him to be thrown in prison and his family (including Airi) to be banished from the imperial court.

Later, Airi's mother died in a carriage accident. The shock of this event worsened Airi's illness and caused her to be bedridden. Airi tried to make Lux angry by refusing his help, but failed. Two months after this, she was sent to stay with a count at the border of the country.

A rebellion occurred, with Lux taking part. Two days before this, he entrusted Airi to the care of a maid to keep her safe. Unfortunately, the emperor Diseld Arcadia (Airi and Lux's father) received warning of the rebellion from a traitor, so he took Airi (unconscious at the time) as a hostage against Lux. She was rescued by Fugil Arcadia, the first prince and another participant in the rebellion. Afterwards, Airi's memories were altered so that she thought she was sleeping in bed throughout the rebellion.

Thanks to Fugil's intervention, the rebellion succeeded and the Old Empire was replaced by the New Kingdom Atismata. As the remnants of the former imperial family, Airi and her brother were pardoned but also charged with a debt equal to a fifth of the national budget. Lux was made to work odd jobs to pay off the debt, while Airi was kept within reach of the new royal family by placing her in the Royal Officer Academy (as a civil official student, due to her weak body ). By using Airi as a hostage, the royal family could prevent Lux from running away or misbehaving. While in the academy, Airi performed jobs such as deciphering ancient manuscripts and updating the Drag-Ride manual, in order to help pay off the debt and to help her brother use his Drag-Ride Bahamut.

Fallen Prince Arc
In Airi's first appearance, she meets Lux after he has been mistaken for a pervert and forced into a duel to redeem himself. She scolds him for getting into such a misunderstanding and says that he needs to win the duel for both of their sakes. She then guides him to the Drag-Ride hangar, teaching him about his opponent (Lisesharte "Lisha" Atismata, the princess of the New Kingdom) along the way.

Airi watches the duel alongside the members of the Triad: Shalice Baltshift, Tillfur Lilmit and Noct Leaflet. While the others are worried about Lux, Airi believes in him. However, the duel is interrupted by the attack of an Abyss, specifically a Gargoyle. Airi remains confident of Lux's strength, believing that he will not lose against the Gargoyle. Lux defeats the Gargoyle with the help of Lisha.

Lux is enrolled into the academy. Airi meets him when he is cleaning the bath and tells him to come to the grand hall of the dormitory. When he does so, she leads him to the dining hall for a party to celebrate his admission.

Several days after the part, Airi goes to Lux's room to wake him up. She criticises him for sharing a room with his childhood friend Philuffy Aingram. Lux explains that the principal Relie Aingram (Philuffy's older sister) is responsible for the situation, so Airi says she should instead admonish Relie. They talk about various subjects, then Airi parts with her brother.

However, the city of Cross Field is attacked by a large Abyss, a Slime, requiring the Knight Squadron to go out to fight it. Lux wants to help as well, but Airi tells him that he can't do anything with just his Wyvern. However, the situation worsens when it turns out that the Slime was merely being controlled by the remnants of the Old Empire, who are attempting to take over the New Kingdom. Lux resolves to go out. Giving in, Airi tells him that she's finished adjusting the output of his other Drag-Ride, but she can't guarantee him more than ten minutes of use. Airi has Noct carry her to the battlefield and they watch Lux fight from a distance. She reveals to Noct that Lux is actually the Black Hero, the legendary figure who singlehandedly defeated 1200 Drag-Knights in the previous rebellion, and his true Drag-Ride is Bahamut, the strongest of the Old Empire's Drag-Rides. She also tells Velvet, the leader of the Old Empire remnants, how he stands no chance against Lux. Eventually, Velvet is defeated and the situation is resolved.

Because Lux is exhausted from the fighting, Airi waits by his side as he recovers. When he wakes up, she hugs him in relief, then pulls away and pretends to act aloof. She scolds him for overexerting himself, both for the recent battle and for the rebellion five years ago. He asks if the others are safe, so she replies that he can ask them himself and she leaves.

Later on, Airi is among the students in the principal's office to welcome Lux as an official student of the academy.

Ymir Nobility Arc
After the red request form incident, Airi remonstrates for Lux getting in a relationship with Krulcifer, but Lux denies it, saying it was all her idea. Afterwards, they were both called by Relli to the secret meeting room below the libary. There they are informed that a special "key" is needed to find the bottom of the ruins, which she suspects is the whistle they confiscated previously.

She later joins the expedition to the Garden as a navigator.

Celistia Arc
After Celistia makes her demand, Airi makes herself clear that she is worried for her brother.

Ries Island Arc
Airi joins the rest of the students at Rias island for training and joins in the search of the ruins. After philluffy was controlled, Airi was able to dispel it by using her own whistle to give philluffy new orders.

Yoruka Arc
The arc begins by Airi warning Lux about the "Empire's Blade". She is also attacked by Greifer after one of his own was attacked.

Class Promotion Exam Arc
Airi travels with everyone else to Vanheim or their promotional exam, there she is cornered and questioned by Shinglen, but she doesn't give in to him. One of the locals overheard that Airi is hiding something and steals her bag and subsequently hides inside the Ruin. Airi recruits the Triad to get the bag back, but before they can they and the thief are attacked by dilwy and subsequently cornered. But Lux manages to make it in time and saves them.

Mel Arc
Airi doesn't make a meaningful appearance in this arc

Campus Festival Arc
Airi works in the libary during this arc. She tells lux to go after Celis after she notices that she is continually following him and to find out what is going on.

Dating Arc
Airi attempts to take up Drag Riding in order to be less of a burden for her brother, but it doesn't work very well.

Rosa Arc
Airi doesn't make a meaningful appearance in this arc

Singlen Arc
After the girls come together for the pact, Airi is instated as the enforcer to make sure the girls to get out of line.

Dragon Marauders Arc
Soffice takes Airi hostage during the reveal, Airi herself attempts to commit suicide with a knife she was keeping on her since the Vanheim incident in order not to burden her brother, but Soffice manages to talk her out of it, saying that she does not intend to hurt her or everyone else around her. She subsequently lets her go after Airi puts the grand force of the moon ruin in place and tells her that she will come to collect her later.

The next time she tries to grab Airi, Soffice is intercepted by Lux and Magialca. Lux convinces Magialca to allow the 2 of them to try and get Soffice to talk. Lux and Airi take turns to guard Soffice, but she herself is uncooperative because it was the old arcadia empire that killed her real sister.

Soffice breaks out during the festival but Airi manages to bait Soffice into revealing herself.

Ouroboros Arc
during the repeated parades, Airi continually observes her brother and scolds him each time he comes back late.

Rebellion Arc
When she realizes that Sacred Eclipse has fused with Queen Raffi, she formally takes up Drag Riding. But not as a combatant but as a situational observer, promising not to move a single step after deploying her Drake.

Abilities
High Drag-Ride aptitude: Airi's aptitude for Drag-Rides is outstandingly high. Unfortunately, she lacks the physical strength and piloting skills to make uses of Drag-Rides. This is why she chose to be a civil official.

Expert Decoder: Airi is skilled at deciphering ancient documents, being on par with the specialist officials of the royal capital.

Strategic Management: She is capable of observing situations and making adjustments mid-battle.

Trivia

 * In volume final Airi finally confesses her love to Lux while he is asleep and gets to kiss him . Airi's behavior is not that strange as Yoruka said, among royalties, marriage between blood relatives isn’t that unusual.