Airi Arcadia is the younger sister of Lux Arcadia. She was originally the princess of the Old Arcadia Empire until she, Lux and their mother were imprisoned but later banished from the empire by her father due to their lack of cruelties towards their subjects. After her mother died, she enrolled as a student of the Royal Officer Academy.
Airi is very calm and collective. She is not terrified when the academy was under attacked by the Abyss caused by Hayes. She is critical to her brother but confident of his strength and worries when he overexerts himself. She has flustered when other people teased her relationships with Lux. Like her mother and brother, she lacks cruelty.