Ailia is the protagonist's personal AI assistant throughout the game. She manifests as a small, holographic fairy during normal gameplay. If the player pursues her hidden romance route, she obtains a full-sized body from Prima Cantor, although her size precludes flight outside of The Unda.

Ailia excels at data collection, automatically updating the player's various Codexes throughout the game. This includes things such as the likes/dislikes of other characters, item drops & drop rates of Dessimals, and more.

In her holographic form, Ailia is incapable of assisting in combat; however, if the player pursues her route, she can accompany the player into Stanzas with the vibe of Mimicry. This vibe allows her to use the combat style of any character or Dessimal the player has recruited. The player can switch her combat style from the menu at any time.

As an AI assistant, Ailia is very personable, although she does not shy away from playful sarcasm.