Hijiri Kasuga

Hijiri Kasuga is a childhood friend and cousin of Arata who disappeared due to a Breakdown Phenomenon after giving the Astil Manuscript to him. She is later on revealed to be a Magus sent by the Royal Liber Academy to observe and elminate him if necessary, eventually returns as a member of Iscariot.

Personality
Hijiri is a cheerful and poised young lady, as well as a strong devotion to those close to her, especially towards Arata. Despite having been assigned as his observer, she cares deeply for his well-being, becoming more concerned of his protection than her own, and even willing to entrust Sora to him before she disappeared due to a Breakdown Phenomenon. As suggested by the opposite of her Thema Ruina, Hijiri is concerned more of others and passionately determined to protect her loved ones. After witnessing Arata's future, she became willing to fight the entire world for him, angry and unforgiving of the world using him as a means to its revival. Often saddened by her current situation, she sometimes will have small periods of extreme vulnerability, such as nearly collapsing in tears after Arata promises to bring her back. Neverthess, she remains incredibly resolute in achieving her goals.

However, Hijiri also has a very cold and ruthless side, willing to go to extremes to accomplish her objectives such as murder or even destroying the world. Surprisingly, she would even attempt to kill Arata and the Trinity Seven, intending to resurrect him after her plans were accomplished. Additionally, she can be quite forceful and intimidating, once almost causing Lieselotte to hesitate in her decision to support Arata. In her initial confrontation against Anastasia-L, their tense interactions would greatly frighten Lugh and Anna's companion. During battles, Hijiri displays a calm and calculating attitude, able to confidently attack and defend against enemies. Although, she can be surprised by any unexpected developments.

While sometimes overly serious, Hijiri is usually quite calm and light hearted, once awkwardly commenting on Arata's perverted antics. Among trusted friends and allies, she is more friendly and approachable.

Appearance
Hijiri is a young slender young woman with short blue hair and a single ahoge on top of her head. She bares a striking resemblance to Arin Kannazuki, but is far more expressive of her emotions. After disappearing due to a Breakdown Phenomenon, her hair grew noticebly longer but has since returned to her original shortness. Additionally, she also has a small  hair clip on the left side of her bangs, but sometimes wears another one on the right side as well.

Prior to vanishing, Hijiri wore a sailor fuku which consisted of a white long sleeved blouse with a sailor collar, a red ribbon tie, a dark pleated skirt, dress socks and penny loafers. After returning as a member of Iscariot, she adorned a short dress under a long sleeve hooded robe, and a hair clip.

Satan: Upon entering this form, Hijiri's hair grows even longer, a crack-like mark appears on her right cheek similar to that of Astral Trinity's, and her hands transforms into large monster like claws. Furthermore, the pupils of her eyes become long and vertical, resembling the pupils of a cat. She also wears a headband, a long dark off-the-shoulder dress worn under a shoulder-less cape held together by a brooch attached to a metallic choker, and a pair of dark slipper shoes.

History
Born into a family of Magus, despite possessing the Astil Manuscrip and Ilias Fragment, Hijiri initially did not realize her lineage and lived a normal life until she enrolled at her parent's affiliated school, the Royal Liber Academy. There, she would also discover that her cousin Arata was a Demon Lord Candidate. As such, at an age of six, she was assigned by the Headmaster to monitor Arata and eliminate him if necessary. However, due to the death of his parents from an airplane crash of unknown causes, her family would take him in and the two would live together. Throughout elementary school, Hijiri would secretly protect Arata against demons, while having Ilia would pose as her. Although she was already more powerful than her parents, Hijiri would be unable to act as a normal girl. Regardless, Arata would continue treat her kindly and she would begin to develop feelinds for him.

During middle school, as Arata had developed a perverted side, she would often encounter various embarrassing situations with him. As such, she would always chatise him, although this also possibly caused him to develop a resiliance at the same time.

Black Sun
One day during high school, Hijiri began hearing rumours of black shadows appearing in town from normal witnesses. Worried over the rumours, she assigned Ilia to impersonate her while she left to school to investigate with Sora. Using her Chaotic Rune to search through the entire city, Hijiri would locate a source of magic at a park, only to witness an ordinary bystander disintegrate into black particles. Analyizing the situation, she would determine if a number of people had already disappeared.

As they traveled around town, they would continue to see more individuals transforming into black particles. After Sora determines that the people disappearing did not possess any magic, she recommends that her master escape before perishing as well. Although, Hijiri remains reluctant to leave, her grimoire warns her that she will be absorbed regardless, as well as being an indirect cause due to her Thema, Ruina,  and connection with Arata the Magic King Candidate whose magic had most likely awakened. Nevertheless, Hijiri remained determined to save Arata at least, and begins searching for Ilia's position. However, upon finding the grimoire, she suddenly hears Ilia cry in distress and begins heading to her location. Finding herself under a highway, the Magus discovers Ilia in her book form, as well as a figure emitting powerful magic. Hijiri quickly notices that the figure is actually Arata, but his magic suddenly causes the Breakdown Phenomen to accelerate and destroy their surroundings. Approaching Arata and taking Ilia, Hijiri then gives Sora to a confused Arata as the situation worsens. After Sora asks her if she is certain, Hijiri confirms her decision, asking the grimoire to her wish and protect him. As the grimoire follows her former master's last command, Hijiri loses her grimoire's protection and begins to disappear. Nevertheless, satisfied with her action, Hijiri leaves a bewildered Arata some last instructions before kissing him, begging him don't forget her. Thereafter, two reach for each other until Hijiri's body envelops into particles of light and vansishes.

After being engulfed, Hijiri would then find herself in an empty world, but is nevertheless satisfied. However, before her consciousness fades away, she witness a future where Arata and the Trinity Seven had destroyed the entire world. Learning of the world's neverending cycle of the Magic King and Trinity Seven to destroy the world, Hijiri became unable to forgive the world for treating Arata as nothing but a tool for its reincarnation. Motivated by this feeling, she would join Iscariot in an attempt to destroy and recreate the world into one Arata could enjoy freely.

Chaotic Rune
Hijiri's Themas are Ruina, Partum, and Analysis of the Ira Archive and her branch of magic is Chaotic Rune, which is based on Norse Runes. Hijiri is a very powerful magus, being able to simultaneously contract with more than one legendary grimore, Astil Manuscript and Ilias Fragment, even before becoming a Magic King Candidate. At a young age, she was already stronger than her parents and fighting against demons. Notably, she once mentioned that she was stronger than Arata, and was even described as Iscariot's trump card to defeat him. As a Chaotic Rune user, she has a tremendous amount of offensive power, as well as a very strong defense. On one occasion, she remained completely unharmed after Lilith attempted a surprised attack on her. Hijiri's Chaotic Rune magic allows her to place multiple runes in different locations as a method to detect any magical activities. She can perform large scale searches by activating them together at the same time. Furthermore, her runes cannot be erased by those with magical knowledge. If necessary, Hijiri can use her concentrate her magic to jump large distances or hide her to normal people, allowing her to move around secretly. Her physical abilities can also be augmented, such as increasing her speed.

After disappearing by a Breakdown Phenomenon, Hijiri received a Magic King Element from the "Ruined World," becoming a Magic King Candidate. However, as result, she can no longer remain in the world for extended periods of time as her body had been broken down by the Breakdown Phenomenon. At present, she is an existence swaying between space and time, taking on the appearance of a gemstone similar to the Magic King Element whenever she is unable to maintain her form.

While considered as a strong magus, Hijiri's Chaotic Rune magic can be nullified by Arin's Demon Spear Gae Bolg. Furthermore, Mira's Gehenna Scope magic has also been noted to be quite effective against Chaotic Rune as well.

Satan
By utilizing her Magic King Element and Trinity status, Hijiri is able to transform to the manifested form of the Ira archive, "Satan", which exceeds the normal Magus Mode. Although, in particular, the transformation itself seems to cause her visible pain. Nevertheless, In this form, she becomes extremely powerful, being able to hold her own against the entire Trinity Seven. Additionally, Hijiri has also demonstrated the ability to break time and space, being able to teleport far distances. She also mentioned that is able to revive someone from the dead using their magic and grimoire, once intending to bring Arata back to life some time later after killing him. Hijiri is capable of forcibly destroying Arin's defensive spells, as well as sabotage her God's Spear Gungir.

Techniques

 * Black Azazel - Discharges a magical blast toward a target.
 * Vegtam - Also known as "Baldr's Blessing", this spell encompasses as both her offense and defense. She may use this spell discharge a magic blast, as well as form a defensive barrier. Arin's Demon Spear Gae Bolg is the only weapon capable of destroying the barrier.

Grimoires

 * Astil Manuscript (Former) - One of the two grimoires Hijiri possessed since birth, Hijiri would give the Astil Manuscript the name, Sora. Sora has a wide range of abilities, including telepathic communication and transformation. Hijiri's Chaotic Rune magic has also been shown to be quite compatible with Sora's abilities, able to help detect magical activities through her runes, as well as projecting images. Furthermore, Sora was also capable of deploying a barrier around Hijiri that would helped her survive the Breakdown Phenomenon had Hijiri not requested the grimoire to protect Arata instead. Their contract would end after Sora formed one with Arata during the Breakdown Phenomenon.
 * Ilias Fragment (Former) - The second grimoire Hijiri formed a contract with birth, Hijiri would also choose the name, Ilia, for the Ilias Fragment. Posessing a wide range of abilties such as telepathic communication and transformation, Hijiri would often task Ilia to impersonate her while she was away. Additionally, due to their contract, HIjiri is connected to Ilia, allowing her to detect her presence by concetrating. Ilia would join Arata after encountering him at the Royal Liber Academy.

Royal Biblia Academy
Arata Kasuga - Initially introduced as Arata's childhood friend and cousin, Hijiri in actuality was sent by the Royal Liber Academy to monitor Arata from a young age. However, this would not prevent them from developing a very close relationship, having a strong understanding of one another. Despite Hijiri's deception, the two have continued to care deeply for each other, willing to fight and protect each other from harm, even after becoming enemies. During the Breakdown Phenomenon that destroyed their hometown, Hijiri prioritized protecting Arata by entrusting Sora to him and instructing her to grant his wish, as well as kissing him before tearfully disappearing while begging him to not forget her. Determined to save her, Arata would choose to become a magus in hopes of bringing her back. Notably, Hijiri, after witnessing Arata's fate in the "Ruined World", would also become determined to protect him as well, joining Iscariot to destroy and recreate the world into one he could enjoy freely. Upon reuniting in spite of being enemies, they were overjoyed to see one another and continued to treat the other in a kind and friendly manner, even after battling against one another. Hijiri, in particular, loves Arata and can become jealous, even sometimes overprotective, of other girls who interact with him.

Trinity S even
Arin Kannazuki - As members of Iscariot and the Trinity Seven respectively, Hijiri and Arin are enemies despite their lack of interactions, as well as rivals for Arata's affection. Most notably, Arin and Hijiri have an unknown connection due to their identical appearances, as well being users of the Chaotic Rune magic. Additonally, they both also possess the Ruina and Partum Themas from the Ira Archive. However, their personalities differ quite a bit as Hijiri displays more emotions than Arin who is much more reserved. The two would first meet during Arata's mission to the Royal Liber Academy where Arin saved Arata and Lilith from being destroyed by Hijiri by using her recently acquired Demon Spear Gae Bolg to break down time to reach them. Arin's Gae Bolg allows her to nullfiy magic from the Ira Archive, making her a natural opponent to Hijiri. Although the two are on opposite sides, they nevertheless have respect for one another due to their strong devotion towards Arata. After Arata is captured by Anastasia-L, Arin agreed to work together with Hijiri to save him, trusting her because of Hijiri's feelings for Arata.

Iscariot
Lugh - As members of Iscariot, Lugh and Hijiri are comrades with the same goal of defeating the Magic King. The two seem to get along well with each other in a friendly and respectful manner, as well as watching over one another in battle. On one occasion, Lugh attempted to defend Hijiri from an attack from Akio despite this eventually to her capture. Lugh, in particular, seems to care for Hijiri's well being, becoming concerned over her unstable health and even willing to fall along with her if she ever tripped, much to Hijiri's astonishment. However, Lugh has also been shown to be intimidated by Hijiri's behavior on some ocassions, becoming frightened during Hijiri's first meeting with Anastasia-L. Nevertheless, the two seem to trust and amiable with one another. During battles, their teamwork has been noted to specialize towards the offensive.

Royal Liber Academy
Anastasia-L - As saints, Anastasia-L and Hijiri have an opposing relation due to their objectives regarding Arata. In their initial meeting, the two would interact with one another in a seemingly friendly and polite manner. However, their tense and hostile discussion of Arata would even Lugh and Akasha's headmaster to become frightened. Nevertheless, Anastasia would continue to treat Hijiri favorably, happily commenting on Hijiri's devotion to Arata. Although, she would also become quickly threatening after Hijiri offered to fight her. As such, Hijiri is especially apprehensive and intimidated of Anastasia due to her dark nature and magic, as well as becoming more protective of Arata.

Trivia

 * Hijiri's manifested form of Ira is a reference to the Biblical demon Satan. According to Christian theology, Satan is often considered the demon most associated with the sin of wrath.
 * In the first print of chapter 0, Hijiri's hair color was initially brown in the color pages. However, in the volume 1, her hair color was changed to light blue which has been used since then.
 * Hijiri is the first girl to ever kiss Arata, and one of only two to have kissed him on the lips.
 * Although, Hijiri and her family possessed magical abilities, her father's brother, Arata's father, and his family were completely normal, with the exception of Arata who eventually awakened as a Demon Lord Candidate.