Masters[]
Arata Kasuga - Prior to Arata becoming a magus, Ilia would secretly take care of him as Hijiri while the real one was away performing missions. After Hijiri's disappearance, Ilia would reunite with him as Hijiri again during his investigation of the Royal Liber Academy's destruction where she would trap him and Mira in her dimensional barrier. Under the orders of Hijiri, she would attempt to convince him to remain with him, enticing him with an image of her as Hijiri in a naked apron before eventually forcibly restraining him. While she would not directly harm Arata, her attempt to kill Mira and imprisonment of Sora would greatly anger him and cause him to transform into Astral Trinity. After being returned to normal, despite her actions, Arata would instead thank Ilia for her care and ask her to join him, which she would happily oblige. Since then, Ilia has become his grimoire, supporting and protecting him through many difficult situations.
Ilia deeply cares and respects Arata, usually treating him in a polite and kind manner. However, she was initially quite possessive of him, but has since mellowed. Although, she continues to become jealous whenever he gets intimate with another girl. Furthermore, while often surprised by his carefree and perverted attitude, Ilia has remained loyal towards him and greatly trusts his decisions. Likewise, in spite of her earlier actions, Arata also cares for her and treats her as a friend rather than a tool which she is especially grateful for. During battles, the two are able to work together as an effective team, using her wide variety of support abilities to help protect him against enemies.
Hijiri Kasuga - Ilia's previous master, Hijiri prior to her disappearance would have Ilia pose as her to take care of Arata while she was away during missions. Ilia would remain with Hijiri after she vanished due to a Breakdown Phenomenon until HIjiri commanded her to lure and trap Arata until she destroyed the world. Although Ilia would eventually join Arata, she is very faithful and cares very deeply for her previous master. After reuniting with Arata, she was willing to kill Mira and other girls close to Arata because Hijiri would be jealous. Likewise, Hijiri did not seem to mind Ilia siding with Arata and would not hold a grudge.
Friends[]
Sora - As former grimoires of Hijiri, Ilia and Sora have known and worked together for an unknown amount of time. The two become separated for some time after Hijiri entrusted Sora to Arata while Ilia remained with Hijiri after her disappearance due to a Breakdown Phenomenon. Eventually, they would reunite again as enemies after Ilia, posing as Hijiri, trapped Sora along with Arata and Mira in her dimension barrier during their investigation into Liber Academy's apparent destruction. Quickly recognized by Sora, Ilia would soon confront her in battle, acting casual and respectful towards one another despite being adversaries. Already familiar with the other's abilities, Ilia, however, would outmaneuver Sora and capture her in the end, intending to use her as a magic source.
Despite Ilia's actions, Sora does not seem to resent Ilia, having any objections to her joining Arata. Since then, the two have remained amicable towards each other, readily teaming together once more to support Arata. While her mischievous and risque behavior often perplexes Ilia, Sora has once stated that this was because they were close enough to never stop fighting. Arata even remarked that the two were actually quite close even though Ilia denies this.
Family[]
Okto - As the third Chapter of the Ilias Fragments, Ilia is the elder sister of Okto, whom she has a cordial kinship with. The two would happily reunite within Dante's Gate in spite of Okto's trail to evaluate Ilia's master's strength. However, the grimoires' reunion would become despondent upon learning of their "mother's" death and the capture of their remaining sisters. Nevertheless, the two would agree to cooperate in order to rescue their remaining family members.
Mina Salem - She is the Witch of Witches and wrote the 9 chapters of the Ilias Fragment. Because she created Ilia and Okto along with 7 other grimoires of the other 7 chapters, she is technically their "mother." Ilia is highly devoted to Mina because Mina created them, but she was shocked after finding out Radix Astil killed the mother she had loved so much.