Yui Kurata

 is the Trinity Seven of the Avaritia Archive and a Cardinal class mage, making her second only to the Biblia's Headmaster. Originally sealed away in a dungeon, she has since been saved by her friends and Arata, becoming a close ally and friend.

Personality
Yui has a very happy and bubbly personality, which often makes her seem childish at times. As such, she is very open with her thoughts, almost always expressing her feelings vocally and physically. For most of the time, Yui is usually excited and joyful, remaining cheerful in even the tensest and dangerous circumstances. Additionally, she rarely holds grudges and thinks ill will of others. After being saved by Arata, she remained friendly towards Mira, who previously was willing to kill her in order to stop her Breakdown Phenomenon. However, her mood can also easily shift depending on the situations, becoming frustrated when things do not go her way or becoming scared when confronted by something she is afraid of. Ironically, Yui is quite frightened by ghosts but finds the monsters are cute. Yui is very friendly and easy to get along with, but notably, due to being placed in the school dungeon alone to sleep, she does not have many friends or close relationships. With the exception of the other Trinity Seven members, specifically Levi, she has remained relatively isolated from people until meeting Arata, whom she has become very attached to. Since then, Yui has become more interactive with her friends, happily playing and enjoying their company. Additionally, she can also be fairly mischievous and daring, often times teasing her friends which she greatly takes delight in. Ordinarily, she is not shy about her body, making suggestive remarks or acting boldly, particularly towards Arata. On one occasion, she independently slept naked in his bed with him. Yui cares very deeply for her friends, willing to fight and protect them from harm. During Iscariot's attack on Biblia, after Levi was defeated by Lugh, she was determined to go and fight by herself, becoming tearful and unwilling to let Levi shoulder the burden by herself.

Yui has also been known to be serious and mature at times. In her first meeting with Arata as her dream form, she acted in a polite and refined manner, helping him discover his Thema. During battles, she can become determined and focused, often times she will support her friends or actively fight herself. Although, she continues to remain friendly and cheerful, even against enemies. Particularly, she has very good teamwork, using her magic to bolster and cooperate effectively with her allies. In the Biblia Magic Research Showdown, Yui, together with Arin, were able to pressure Arata and Lieselotte for the majority of the match, and eventually defeat them to win.

As she disregarded and isolated herself from others her research Thema is Amicitia (Friendship) of the Avaritia (Greed) archive. In the fight against Farfarella, despite being saved, Mira is scared of her. Knowing that Yui's theme is Friendship, Yui actually doesn't care even if Mira is actually killed and not just from illusion.

She revealed to Arbariccia during their fight that she doesn't have friendship because she is not real. In her Last Crest, Yui is shown sleeping and dreaming in her own dream world, and she herself is not sure if her dreaming self is not itself another dream, that continues infinitely. Likewise, the world where she is a Trinity Seven could also be just another dream.

To her, the only thing she believe to be real is Arata.

Appearance
Yui is a well endowed young woman with shoulder length grey-white hair with a single ahoge. Possessing the Phantom Cross eye, giving her distinct yellow eyes with cross-shaped pupils that can change color. Her hair is normally tied into pigtails held together with pink ribbons, along with three pink heart-shaped hair clips on her bangs.

Some time after Arata departed to train at the Royal Arkasha Academy, Yui began to styling her hair into pigtails fastened by dark bands.

She generally wears her school uniform, which consists of a white collared shirt worn under a dark blazer jacket with cuffs and the school insignia on the left breast pocket. The lower half includes a plaid mini skirt, black dress socks, and brown loafers.

Magus Mode: Yui wears a white, sleeveless collared tail blouse with white laces on the bottom hems. Additionally, she now wears opera gloves with white cuffs that are pink from the arm to the wrist and black onwards to the hands. She also wears the same plaid mini skirt and brown loafers, but with thigh high socks with cuffs that are white from the ankle to the foot. Lastly, Yui also wields a white conductor baton in this mode as well.

Dream Form: In her dream form, Yui transforms into an idealized older version of herself, becoming taller and her bosom also notably grows bigger. Furthermore, her hair grows longer as well, now covering her back. Originally, she had her bangs tied together with a rubber hair band and did not have her three heart shaped hair clips. However, since then, she currently styles a small ponytail on her upper left side with the heart shaped hair clips.

Anime = Manga =  Yui dream form ch4 MA.jpg|Dream Form Yui_pigtails_ch63_7M_MA.jpg|Post Time-Skip

History
Due to her immense magical abilities, Yui was sealed by Master Biblia in a dungeon under the Royal Bilbia Academy where she would sleep and research in her dream world.

First Friend
One day, Yui is visited by a young girl named Levi who asks if she wants to be friends in the real world. Upon bringing Levi into her dream world to discuss, Yui is initially disinterested in the idea of friends and the outside world due to them being unnecessary. Nevertheless, Levi manages to entice her curiosity by explaining the fun and useful purposes of friends. Formally introduce themselves to one another, the two become friends.

Afterward, Yui would occasionally be visited by Levi in the dungeon, but otherwise, she remained isolated from the outside world.

Meeting Arata
Arata met her when she saved him from being killed by Akio to stop the breakdown phenomenon. She pulled him into the dream world at the last moment. There she introduced herself and explained to him what archives and Themas were.

When Arata met with her, the power of the magic king affected her. Causing the entire school to go to sleep as part of a Breakdown Phenomena.

Arc Symphony
Yui's Thema is Amicitia from the Avaritia archive, and her magic is Arc Symphony. As a Cardinal class mage, she is one of the strongest mages in Biblia Academy, being second only to the Headmaster. However, because of her immense magical powers, if left unrestrained, she becomes capable of creating a Breakdown Phenomenon that can put the entire world to sleep and eventually destroy everything. During her own Breakdown Phenomenon, a dragon, considered to be a very high-level monster, would even appear. As such, she was originally sealed away in a dungeon under the school by the Headmaster where she slept and lived in her dream world.

Yui's Arc Symphony grants her the ability to create her own world and control any aspect within it. Inside her dream world, she is able to use her full power such as altering dimensions, creating different types of monsters, allowing access to her world and even change her own appearance to an idealized version of herself. Although, if she becomes upset, she cannot maintain the image and temporarily reverts back to her true form. Furthermore, she can directly effect affect the real world as well, such as physically pulling people into her dream world, directly communicate or project an astral image of herself in the real world to support her friends and allies. Her ability is powerful enough to drag people into her dreams without them realizing. While Arc Symphony is not entirely suited for direct combat, Yui especially excels in defense, support, and buffing magic, putting her magic in a different class of its own. Using Arc Symphony, she can greatly increase Akio's Mantra Enchantment power or even enhance Arin's Chaotic Rune to achieve the Trinity. As such, her support magic and good teamwork make her an ideal partner in battles. Yui's defensive magic allows creating barriers that can block both physical and magical attacks. She is also capable of creating a large barrier strong enough to protect even a stadium of people from a Breakdown Phenomenon. Yui has also been shown to be able to remain mostly calm in dangerous situations. Moreover, Arc Symphony even allows her to stabilize rampaging magic such as Selina after she had her magic stolen by Lieselotte.

Additionally, Yui also has the ability to summon monsters indefinitely to do her bidding and instantly create large barriers that replicate her dream world in the real world. In particular, her barrier is said to contain an enormous amount of magic that not even Lieselotte is not able to fully analyze it and even amaze Ilia. As long as she is within her barrier, Yui is able to use her full strength and perform spells similar to Arata's world reconstruction magic. This allows her to hold her own in a fight despite specializing in support magic. Yui has also demonstrated the ability to conjure musical pieces that can physically bind and constrict an opponent

Although Yui does not possess high physical abilities, she can render her opponent asleep with a single strike. Also, as a Cardinal Class-mage, she is strong enough to beat 2 members of Malebranche in an instant. Although, this is also boosted by the nature of magic power in Dante's Gate that gives more power to those who does not desire it, and Yui's archive, Greed, fits it.

As a possessor of the Phantom Cross Eye, Yui has the capability to send anything into a riff between dream and reality.

Outside of magic, Yui is also a skilled violinist.

Techniques

 * Starry Night Serenade - A spell that pulls others into her dream world where she can make them fall asleep with a dream of her choice, or both.
 * Dreamy Fairy Serenade - A large area sleeping spell, Yui summons multiple creatures with the appearance of musical notes with wings to do her bidding. Anyone with low magic who comes near them falls asleep.
 * Shift Change - Yui reconnects to her archive and transforms into her dream self which allows her to use more powerful magic.
 * Meteor Symphony - A spell similar to a meteor shower that rains down star-shaped objects at Yui's target. The name is borrowed from Arata's "Meteor Dragonar"; which Arata used to suppress Yui's Breakdown phenomenon and save her.
 * Fury Combat March - Generates waves of sounds to augment the magic of those around Yui.

Combination
 * Hymn & Holy Seal - By enhancing Chaotic Rune's Holy Seal with Arc Symphony's Divine Song macro, Arin and Yui are able to create a barrier capable of destroying Arata's Meteo Dragonar.
 * Khachaturian Orquesta - Yui creates numerous musical notes that pierces her opponent's body. She claims that she used Arata's change into a "Sword Magus" as a hint to create it. She uses it to finish off Falfarea after discovering his real body.

Grimoire

 * Aleister's Score

Royal Biblia Academy
Arata Kasuga - Yui first met Arata after she saved him from being destroyed by Akio's attack, pulling him to her dream world where she helped him discover his Thema. An early ally of Arata, the two of them easily get along with each other, even calling him big brother in their first meeting. Since then, they have become good friends despite only knowing each other for a short time. Yui falls in love with Arata, growing extremely attached to him after he helps save her from her Breakdown Phenomenon. As such, Yui greatly enjoys being with him, finding his open and straightforward personality amusing and fun. She is especially forthcoming to his perverted antics, often proposing risque comments or encouraging suggestive actions. On one occasion, she slept next to him along with Arin naked. As a result, Yui can usually feel frustrated and jealous whenever he interacts with other girls, with the exception of the Trinity Seven to a certain degree. After seeing his attention to Anastasia, she would become nervous and envious, promptly stating that she would do everything with him. Likewise, Arata greatly enjoys her company and affection, finding her cute and attractive. Additionally, in spite of her willingness, Arata does hold himself back on certain occasions. When offered the chance to kiss her, he refused and stated that that was something for when they were closer. Nevertheless, they both care very deeply for each other, happily willing to support and fight for one another.

Trinity Seven
Levi Kazama - Out of the Trinity Seven, Levi is Yui's closest friend due to the natures of their Themas. During her time in the dungeon, Yui was often visited by Levi who would keep her company and watch over her. When she started a Breakdown Phenomenon, the casual Levi would then become very determined to save her. She would even choose to fight against Akio, in order to stall Grimoire Security. The two of them normally get along very well as a result of their cheerful and nonchalant nature. In almost any situation, they are usually playing along with each other and enjoying the moment. They both care very deeply for one another, willing to fight and protect each other. After Levi was defeated by Lugh, Yui became determined to go fight herself, unwilling to let Levi shoulder the burden by herself. During battles, they are able to work together and support each other to overcome dangerous situations.

Arin Kannazuki - Yui and Arin view each other as good friends and reliable allies, despite their mutual interest in Arata. Nevertheless, the two care for each other and are willing to fight to protect one another. During Yui's Breakdown Phenomenon, Arin helped save Yui from the illusion dragon. Since then, they have gotten along very well, teasing and enjoying each other's company. Notably, they are often seen together with Arata, although they continue to remain friendly with each other. In particular, Yui has declared that she was fine being his mistress while Arin remained his wife. Likewise, Arin also stated that she was mostly fine with him being with the Trinity Seven. In battles, the two of have proven themselves to be a very strong and effective team. During the Magic Research Showdown against Arata and Lieselotte, Yui and Arin were able to greatly pressure them for the majority of the match and eventually defeat them when Yui helped Arin achieve the Trinity. Their teamwork has been described as specializing in defense.

Mira Yamana -She originally wanted to get rid of Yui for causing a breakdown phenomenon, as it is her job, and over time they have become friends.

Trivia

 * Prior to leaving the dungeon, Yui's Magus Mode had never been revealed to anyone.
 * Yui is one of two members of Trinity Seven to have caused a Breakdown Phenomenon.
 * At the age of 14, Yui is the current youngest member of Trinity Seven.
 * It is revealed in the light novel of the series that Yui isn't her real name.
 * Yui has a very similar manga counterpart in the manga Countrouble by the same artist. They look very similar however the character has one of her eyes hidden by her hair
 * Yui's hair in her dream form is similar to Mirajane Strauss from Fairy Tail.