Arin Kannazuki

 is the Trinity Seven of the Ira archive and a user of Chaotic Rune magic, whose appearance is strikingly similar to Arata's childhood friend Hijiri. Furthermore, she is also the Magic King's partner, becoming an early ally and later close friend to Arata.

Personality
Arin is quite blase, typically only having a serious or blank expression and rarely showing any other emotions. Because of this, many of her actions and expressions usually do not match. Furthermore, Arin has often been shown to be blunt and lack common sense, generally never reacting the same way most people do in many situations. For example, Arin on one occasion chose to bath in the male bathroom because she preferred the quiet. Even when Arata discovered her naked by chance, she barely showed any reactions and acted nonchalant despite his presence. Often times, others have to correct and chide her for her behavior, which she usually finds difficult. However, despite her lack of expression, Arin is not quite a cold as she appears to be. In actuality, she can be kind and caring, even if she does not show that often. Arin gets along very well with her friends, caring for their safety and willing to fight for them. She has also been shown to be perceptive, once immediately noticing Mira's change of attitude towards Arata.

Notably, prior to meeting her partner, Arin has been noted to avoid interacting with others in favor of focusing solely on her research. However, since then, others have observed that she is more expressive and social towards those around her. In particular, she has become very devoted to Arata, supporting and protecting him whenever possible. Arin can also act jealous when he interacts with other girls; although, she does not mind him being with the Trinity Seven.

Appearance
Arin is a petite, slender young woman with short light blue-gray hair and a single horn. Notably, she also bears a striking resemblance to Hijiri Kasuga. However, Arin normally has an emotionless expression, rarely changing her expressions. Although, since meeting with Arata, she has begun to show a wider range of emotions. Her usual outfit consists of her school uniform, a white collared dress shirt worn with a dark blazer jacket with the school emblem, and a plaid mini-skirt. She also sports a plaid cravat bowtie, black knee-length socks, and loafers. On her left ring finger, she wears a simple band ring with rune inscriptions that are seen when activating her magic.

Magus Mode: In her magus mode, Arin switches to a dark one-piece mini dress under a long sleeved hooded robe with white lace trims and tied with a thin red ribbon in a cravat knot. Her socks and shoes remain the same.

History
Unable to remember her name and origin, much of Arin's past remains a mystery to even her. Her earliest memory is when she was around eight years old, she was shrouded in darkness before growing conscious of her existence. She would suddenly find herself in an unknown location and become first aware of the world around her, which the experience would cause her to cry. Later, while wandering around, she would meet the Biblia headmaster who told her that he had come to pick her up. Bringing her to the Royal Biblia Academy, the two would encounter unknown monsters that no one else had previously seen before. Although some of those monsters were easily defeated, there were also several that they were forced to flee as suggested by the headmaster despite his Paladin class.

Eventually, she would arrive and enroll at Biblia, as well as becoming a member of Trinity Seven. Notably, during times she left the Academy grounds, the previous unknown monsters would appear again outside the academy.

Meeting Arata
The first encounter between Arata and Arin would be in the Male's bath, where Arata would mistake her for Hijiri during their initial encounter. It is from then on she would begin to experience emotions that she had never felt before, such as attraction towards him, going as far as stalking him for much of the next day.

Abilities
Priestess of Yggdrasil - Both Arin and Hijiri are special entities, the Last Key. Their existence is needed to be able to reach the core of True Demon King, thrown away into the furthest end of dimensions. It is because of this ability Arin and Hijiri are able to reach Arata who is sealed by Anastasia in the Terminus Library.

Chaotic Rune


Arin's Thema is Ruina from the Ira Archive, and her branch of magic is Chaotic Rune, which is based on the ancient writing style Norse runes. Specifically, Chaotic Rune manifests the power of gods into runes, capable of overpowering Magic King magic once enhanced. Using macros recorded in her grimoire Laguna Yggdrasil, she is able to perform a wide variety of spells both offensively and defensively by drawing symbols with her finger. Additionally, her magic is also considered to be one of the more destructive ones out of the Trinity Seven. In one instance, she was able to forcefully remove the Astil Manuscript's restriction on Arata, causing his power to become unstable.

Upon receiving the Demon Spear Gae Bolg due to her desire to protect Arata, Arin's magic abilities increased even further, even once breaking down time and space to teleport herself. Her offensive abilities, in particular, also further improved, able to outclass melee-types now despite once being only spell oriented.

Chaotic Rune has also been shown to be very compatible with Yui's Arc Symphony. By combining her spells with Yui, her magic is greatly enhanced, to the point of stopping a Magic King Candidates attacks. Furthermore, upon transforming Gae Bolg to God's King Spear Gungir, she can achieve another third of the Trinity. With Yui's Arc Symphony supporting her magic, she gains the Thema Victoria allowing her to complete the Trinity. At this stage, she has a very staggering amount of magic that becomes difficult for her to control.

During battles, Arin usually remains very composed, able to calmly and intelligently fight against her opponent. On rare occasions, she can lose her focus in dangerous situations involving her friends, especially Arata.

Arin is also capable of creating a Breakdown Phenomenon with the same destructive force as Arata's after her magic clashes with Hijiri's. Afterward, she can access the Breakdown Phenomenon's world where she can locate individuals through their magic

Techniques

 * Arin_Eiwhaz_F1_MV.pngTiwaz - An offensive spell that shoots magic energy that is capable of destroying a boulder. This rune can also stabilize the utilization of magic powers, as well as enhance other spells.
 * Sowelu - A light spell.
 * Eihwaz - A defensive spell that is able to ward off shadows and block physical attacks. This spell can be placed on other individuals, as well as summon a bow.
 * Kano - A flame spell
 * Uruz - Temporarily augments Arin's magical power to Yui's cardinal class level. However, there is also a risk of her degrading into a monster if she runs out of magical power.
 * Fehu - Summons an arrow of light.
 * Othala - Returns a target to it's "homeland".
 * Raidho - Manipulates the magic within a Magus' clothes around Arin to transform into different articles of clothing of her choosing. However, after a certain duration, the spell loses effect which results in the clothes dissipating.

Weapon

 * Arin_mistilteinn_ch28_7M_MA.jpgSecret Art of Mistilteinn  - Using Gae Bolg, Arin performs a strike that creates a powerful magical blast capable of even destroying Hijiri's strongest defense, Baldr's Blessing.
 * Limit Release - Transforms Gae Bolg to Gungnir
 * Valfodr Inferior - Upon achieving the Trinity by wielding Gungir and gaining the Thema Victoria with the support of Yui's Arc Symphony, Arin inserts all of her magic into Gungir and throws the spear to explode after contact. Even withholding the power was enough to render anyone unconscious.
 * Perfect Guard - One of Gae Bolg's Armed Skills, the spear is able to consciously protect a target, allowing Arin to move at speeds rivaling even Lugh's.

Combination

 * Hymn & Holy Seal - By enhancing Chaotic Rune Holy Seal with Arc Symphony Divine Song macro, Arin and Yui are able to create a barrier capable of destroying Arata's Meteo Dragonar
 * Hagalaz - Together with Hijiri, creates a large rune on an object before breaking the same object.

Grimoire

 * Laguna Yggdrasil - Having the appearance of a book, Laguna Yggdrasil contains all of Arin's macros which she can activate her magic spells. Normally, Arin usually has her grimoire change to the appearance of the ring she wears on her left hand. Notably, inside Laguna is the World Tree Library, a divine place created by Scathach that stores all knowledge of runes and supposedly vanished in the Ragnarok. Arin was able to access the Library by pouring her Ruina magic into Laguna and gain possession of Gae Bulg.

Weapon

 * Arin_Magus_Mode_Gae_Bolg_ch42_MN.jpgDeath Spear Gae Bulg - Due to her desire to protect Arata, Arin traveled to the World Tree Library where she received the Magic Spear Gae Bulg, which originally belonged to Scathach, the founder of Chaotic Rune magic. Upon forming a pact, the wielder is granted enhanced magical power, as well as the physical abilities on the same level as a martial arts expert. As such, even ordinary mages can become masters simply by possessing Gae Bulg. However, if the owner breaks the pact, a curse is invoked that will destroy it's master's heart. This spear also has the ability to nullify magic from the Ira archive and even allow her to break time and space on one occasion. As such, Gae Bulg is said to be so powerful it can pierce any defense. Additionally, the spear is a cornerstone for Arin's Partum Thema, allowing her to achieve the Trinity.
 * God King Spear Gungir - Upon invoking Limit Release, Gae Bolg will transform to Odin's Armament, God King's Spear Gungir, an anti-Magic King Weapon. In this form, Arin's magic power is further significantly increased. Additionally, Gungir allows her to complete another third of the Trinity.

Royal Biblia Academy
Arata Kasuga - As the partner of the Magic King, Arin cares very deeply for Arata and as well loves him, becoming quite attached to him since his arrival. She often calls him her husband and considers them to be already married. Arin first met Arata in the men's bath unclothed, although she was rather nonchalant during the whole experience. However, because of the nature of their relationship, Arin developed a strong interest in him mainly for her research. While on the other hand, Arata was unsure how to interact with her due to her blunt personality and identical appearance to Hijiri. Regardless, the two of them quickly became good friends, even after Arin trapped him or even caused him to create a Breakdown Phenomenon. Arin does not mind Arata's shameless personality, even willing to comply with some of his desires. Likewise, he has also become used to her, appreciating her support and guidance. Although, they sometimes still find aspects of each other surprising and troublesome as well. Notably, since meeting Arata, Arin has slowly begun to change from her usual emotionless behavior, showing more different emotions which have been noticed by her friends. Both of them genuinely care for one another, willing to support and protect each other during dangerous situations. Arin's attainment of the Demon Spear Gae Bolg was largely due to her determination to protect him. Also, Arin can become jealous whenever he interacts with other girls but is more or less fine with her friends in the Trinity Seven.

Trinity Seven
Lilith Asami - As members of Trinity Seven, Arin and Lilith are good friends and usually get along very well. Although, due to Arin's straightforward character and lack of common sense, Lilith often times has to correct her actions and behavior, which Arin usually finds difficult. Despite this, the two of them care for one another, willing to fight and protect each other. Furthermore, while Arin is sometimes jealous of Lilith's closeness with Arata, she actually does not mind and both of them continue to remain on friendly terms.

Yui Kurata - Yui and Arin are good friends, both willing to fight and protect one another. When Yui's magic becomes unstable and causes a Breakdown Phenomenon, Arin is one of the people who helps save her. Also, despite the two being interested in Arata, they still remain on a friendly term. Although they sometimes get jealous of each other's interactions with him. At one point, Yui has stated that she was willing to be his mistress because Arin was his partner. During battles, both of them have been shown have excellent teamwork as their magic complements each other. For the Magic Research Showdown, they were paired together as a team and faced off against Arata and Lieselotte. With their combined efforts, they would control the majority of the match and greatly overwhelm their opponents. Finally, Arin, with the support of Yui, would achieve the Trinity, defeating Arata and Lieselotte. Their teamwork has been noted to specialize in defense.

Iscariot
Hijiri Kasuga - Arin and Hijiri are believed to have an unknown connection due to their very similar appearances and magic. Both of their Thema's are Ruina from the Ira Archive and they also utilize the same Chaotic Runes magic. However, their personalities are quite different as Hijiri displays more emotions than Arin. Furthermore, as members of Iscariot and the Trinity Seven respectively, Hijiri and Arin are enemies although they are willing to work together due to their strong devotion to Arata. When Hijiri was about to destroy Arata and Lilith, Arin gained the Demon Spear Gae Bolg to break down time and space in order to save them. On another occasion, after Arata became trapped by Anastasia-L, Arin willingly agreed to ally herself with Hijiri regardless of her past actions, trusting her rival because of her real feelings. While the two girls are competing for Arata's affection, they nevertheless have respect for one another. Notably, despite their interactions, neither of them have commented on the unusual circumstances behind their identical appearance. Furthermore, Arin's possession of Gae Bolg allows her to nullify magic from the Ira Archive, making her a natural opponent to Hijiri.

Trivia

 * Arin's Demon Spear Gae Bolg is a reference the Irish mythical weapon of the same name. The founder of Chaotic Rune, Scathach, also shares the same name as the Irish woman warrior who gave Gae Bolg to the hero Cuchulain.
 * Gae Bolg's second from Odin's Armament, God King's Spear Gungir is a reference to the Norse mythological weapon of the same name wielded by Odin. Odin, known as the god of Death and All-father of the gods, is also old Norse for the "Furious One", which is a reflection of Arin's Archive Ira, or Wrath.
 * In the initial print of chapter zero, Arin's hair is colored brown in the color spread. However, in volume 1, her hair color has since been changed to her current color, light blue.
 * In the first anime commercial, her bust size is stated to be 83 cm. However, in both episode one and chapter one, she tells Arata her bust size is 82 cm.
 * The anime promotional material puts both Arin's and Yui's bust size at D, even though Arin's manga appearance is much more modest. Arata himself has compared their drastic size difference when both of them slept naked next to him.