She is Kazuki's mother. During the story she was referenced many times by Kazuki, Liz, and many other characters. In order to protect Kazuki, she abandoned him in front of the Nanohana House's gate and fought against Loki, resulting in a mutual defeat. What she didn't know before her demise was that her abandonment left a scar in Kazuki's mind. This was demonstrated throughout the story, specially when Kazuki fought against Miyabi.
She encountered Kazuki when he and his companions were in the Mt. Fuji Haunted Ground. She reacted to his presence and aided him in his battle against Ilyaelia. After his battle, she encouraged her son to reach the top of the mountain and claim the Kusanagi. She appeared briefly again when Kazuki was cooking in an igloo and engaged in a conversation with her son. It was revealed that she deeply regretted many things, one of them is not being able to teach her own cooking to her son.
When he reached the summit of Mt. Fuji, she tested him. Surprised by his skills, she revealed everything she knew about her connection with Kazuki, and instead of being the target of his rage, he thanks her. After that, her soul was almost consumed by Hel. Unable to maintain her form, she gave Kazuki the Kusanagi and spoiled him for a bit. Then, she conveys her light particles to his chest and leaves the world with some words of encouragement, saying that from now she will be together with him.
He likes Miō and tries to protect her at all costs, he seems to care a lot about her because she was the most important person to him in the Nanohana House. In the beginning of the story, she acted as a girl who hated him because he is the only man in the Magic Division and an E-Rank Summoner. Later, it was revealed that the only thing that she hated about him was his adoption by the Hayashizaki family. She said that out loud without caring the consequences and was challenged in a duel by an enraged Kazuki. He defeats her and mends her relationship.
After that event, her attitude towards him changes and reveals her "dere" side to him. She loved him so much that she used her body to protect him from a fatal blow from Loki and died. Kazuki, angered for his weakness, tried to find a way to revive her. He succeeded by using Phenex's Revival magic and collapsed from magic intoxication. After this event, her love for him increased.
She is also the first girl that got 150 positivity points. She usually spends her mornings trying to seduce Kazuki with maid clothing that she designed especially for Kazuki's eyes. Also, she is the cause of his maid fetish. Her animal is a cat that says "meow".
She is an orphan from the Nanohana House. She considered Kazuki as her brother during his stay before his adoption by the Hayashizaki family. After some time, when he and Mio left the orphanage, she felt alone and because of that she became the target of Loki's antics.
Her personality and body changed throughout the time, including her opinion about Kazuki and Mio. She encountered Kazuki when he was in a date with Mio. She appeared again after his duel with Iori, lost control of her powers and accepted her new contract with Loki.
During Kazuki's battle against Beatrix, she aided him in his escape and made a truce in order to defeat her. Before the battle it was revealed that no matter what he did, he usually received a skull mark from her, indicating that his relationship with her was more strained than he thought.
After Kazuki's second battle with Beatrix and Nyarlathotep's clash, she became the main antagonist with Loki. She was one of the perpetrators of the civil war and Yamato's uprising. She encountered Kazuki again and after a confrontation of ideals she ended her relationship as Kazuki's little sister and engaged him in a battle, resulting in her defeat and escaped from the oncoming front war.
Kazuki sees Kanae as his little sister only, Kanae always tries to seduce her "Nī-sama", but her attempts were useless so far. She also hates every other woman who is around Kazuki unless she accepted them as "strong" to stand by his side. She didn't acknowledge him as a student from the Magic Division at the beginning and tried to take him to the Sword Division by making him fight in an official duel as a summoner. After she saw his win over her student, she recognized him as a summoner and engaged in a battle with Kaguya against Kaya's dragons.
During the events from Volume 9, it was revealed that she can only fight seriously if her opponent is only Kazuki. She can't fight at her 100% with another opponent even if her life is in danger or the world collapses. It was later stated that Kazuki was aware of Kanae as a woman in the past and was resisting every attempt she made thus far. This time, her last attempt succeeded and kissed him for a long time.
Kazuki likes Kaguya a lot because she was the first person to greet him to the National Knight Academy. He has a lot of respect for her as the strongest student in academy as well as the Student Council President of the Magic Division. His respect and affection for her was so deep that he did not want to engage in a serious battle against her when she was controlled by Nyarlathotep. In Kaguya's mind, she reciprocates those feelings too. Asmodeus even stated that because of her feelings, she can't hate him, thus he can't be Guernica's target.
After those events, both mend their relationship and from then she tries to seduce him without trying to kiss him. The reason of this restriction is because of the one time use of her level 10 incantation. In Volume 10, that restriction disappears because Kazuki used that last resort to defeat his enemy.
Every time Kaguya uses Asmodeus' powers, she enters in a state similar to someone drugged with aphrodisiacs. In order to calm herself, she goes to Kazuki's room at night and "plays with him" until the effect disappears. There are some cases where Asmodeus' effect are not instantaneous and it triggers when Kazuki is in the middle of an unfortunate situation. This usually suggests two things: Asmodeus is controlling the after-effects in order to prank her King through Kaguya, or Kaguya can control or hold off the after-effects for a certain amount of time.
At first Kazuki saw her as a cute girl, but later he understood that behind her coldness she is just lonely and misunderstood. After the events of Nyarlathotep, her cold personality disappears and begins to open up, especially to Kazuki. Later in the story it is revealed that she likes to be threatened by him and encourages him to do things that puts her in an embarrasing situation. When she feels upset, she usually pouts and murmurs "puu", which is the sound of a rabbit.
During Kazuki's speed chanting training, she used telepathy and made many mental messages to Kazuki. To increase the difficulty, both of them began to flirt to the point where both kissed for a long time. She took advantage of this to convey her feelings by making a great amount of mental messages saying "I love you".
Kazuki seems to respect Hikaru as her Kouhai, he also taught her swordsmanship. She initially believed that he was a woman the first time she met him in the Witch's House, saying that she was not the only tomboy of the group. After learning that he is a man, her androphobia was revealed.
He wants her to get used to being around boys. After her defeat by Mibu's team, Kazuki asks her on a date in order to relieve her from her androphobia. During the date, he made her realize that she was a woman by kissing her, making her wear a dress and watching a romantic film.
From the results, he succeded, and unfortunately for him she becomes an open-minded pervert. From then, she usually tries to tease Kazuki through bold actions (such as rubbing her body to his chest, sneaking into his bed, kissing him every time she finds an opportunity, etc.)
Leme naturally likes Kazuki because he is her "King", she also wants her "harem plan" to come true. She is very open about her desires. It was later revealed that she liked his late mother (and former contractor). She chose Kazuki as her mother's succesor even before his birth, and through the years she was watching him in order to become what he is now. It is later suggested that she may like him more than he thinks.
She always takes advantage of him (she appears everytime there is food, she sleeps with him when he is alone on his bed, by using her adult form she teases him during his mornings, etc.), but this demonstrates how much she cares for him.
Kazuki is very protective of her because of her past as shown when he became furious that Charlotte has to be executed. At first, she saw him as a brotherly figure, and after her date with him, she develops feelings for Kazuki, saying that she would like to be with him for more time. During his second battle with Beatrix, she tried to surrender in order to make her spare Kazuki's life. This led him to kiss her, engage in a battle with Beatrix again and defeat her.
By fulfilling his promise that he would protect her no matter the cost, she finally fell in love for him. She usually tries to gain Kazuki's attention using her doll-like appearance and innocence. It is stated that sometimes she watches anime with him, and later with Itsuki. She prefers to be called Lotte.
Kazuki maintains a teacher-student relationship with her. Although she usually calls him trash, she really cares for him. When she discovered that Kazuki's mother was her best friend, she helps him find the Kusanagi in Mt. Fuji. After some events, she asks him to conquer her.
Kazuki doesn't seem to dislike her, but he strongly disagrees about her views of marriage just for the sake of uniting two styles together. After this incident, she tries many ways in order to gain his attention (for example, talking to him as bosom friends). Kazuki respects her as a swordsman, and finds her innocence quite amusing.
Kazuki acknowledged Beatrix as a very strong opponent and seems to be on neutral terms with her. After further interactions with her he doesn't seem to mind her presence and are on friendly terms with her, he also starts to call her Beatrix-chan because she wanted Kazuki to address her that way. It is later stated that Beatrix fell for him so hard that if he loses his status as a King, she will take him to Germany and marry him.
During her debut in the story, she attacked Kazuki when he was in a date with Mio and almost kills him. After her failed attempt, she tried to assassinate Kazuki again, but this time he was prepared and defeated her. Her third assassination attempt was in the Chief Student Council Battle Election. She lost again, but this time, her sister abandoned her. Depressed and alone after what her sister did, Kazuki tried to cheer her up and succeded. Like Lotte and Itsuki, she likes watching anime.
Initially, she disliked Kazuki because from her perspective he was snaring girls for his own desires. Later in the story, she learns that he does that in order to protect the girls and the academy. She tried to apologize to him, but because of her shyness, she couldn't say the exact words and tried to change the subject or simply acted as a tsundere and mocked him. During the infiltration in Volume 6, her feelings for Kazuki were revealed by Itsuki's influence. She confessed to him and became a "dere" character.
At first, Kazuki saw her as a mysterious and bold woman that asked him to conquer her, but after some time it is later revealed that she was mentally scarred because of her transformation to an elf during her childhood. During the events of Volume 8, she falls for Kazuki and begins to open up more without remorse. With her twin sister Shinobu, they try to seduce him using the "sister sandwich card".
During her debut in the story, she despised every character that tried to be in her sister's way, or at least that was what she thought. She disliked Kazuki because Miyabi talked to him during the Chief Student Council election, and after her battle against him, her dislike grew more. It was later revealed that she did not hate Kazuki because she was in a state where everything that is not her sister is worthless. This was caused when Miyabi went through the elf transformation. During and after the Mt. Fuji treasure hunt, she breaks her shell and with her sister's help, apologizes to Kazuki and develops feelings for him. After that incident, she and her sister try to seduce him. While Miyabi flirts with him using bold methods, Shinobu seduces him with cute actions (for example, kneeling down and showing her puppy eyes, or in this case, the eyes of a wolf pup).
Kazuki encountered her when she was only a spirit without a body (she was killed by Ikōsai). She is too shy and hates meeting new people. Before her debut in the story she was a NEET that depended too much of her parents. After the events of the infiltration, she tries to take actions by her own, but it usually ends in a failure. Kazuki encourages her to continue doing it and with Lotte and Karin's help, her personality changes a bit.
Akane maintains a Senpai-Kouhai relationship with Kazuki. During her debut, she was one of the commanders of the Knight Order that went to battle in the civil war and acted as the tsukkomi of her friend Kanon. She envied and respected Kazuki because of his skills and success during his surprise attack with the students of the Knight Academy. Later, her respect increased when she heard of Kazuki's feats.
She was later introduced again during the trip to America as the captain of the ship and the one who offically named the ship "Queen Kaguya".
Like Akane, she maintains a Senpai-Kouhai relationship with Kazuki. She is usually cheerful and acts as the comic relief of the group. She was the student council president of the Magic Division, which means that she is proficiently skilled with her powers.
However, despite her suggested skills, her learning capacity is below average. It is demonstrated when she became one of the sailors of Queen Kaguya. Even when everyone of the crew passed the entire class (Akane spent days without sleeping in order to become the captain), she only learned half of it.
Kazuki encountered Ikōsai during the infiltration in the civil war arc. She was a dangerous opponent to Kazuki because her assassination technique with the sword could not be seen by normal eyes. In their first fight she almost defeats Kazuki, but because of her lack of experience, she loses the oncoming rounds. Her lack of battle experience is later hinted in later battles against Kazuki. Despite being more skilled with the sword than Kazuki and being able to chant faster than him, her arrogance and lack of experience led her to develop an inferiority complex towards the Kings, especially Kazuki. To overcome this, she pursued power so agressively that she didn't care about the consequences of using said powers. During her final battle against Kazuki, her control over Susanoo falls. Her body would have been hijacked by Susanoo if Kazuki didn't hit her with his newfound sword technique. After her last defeat, she is imprisoned.
Kazuki admired her skills to the point that he said he "fell in love" with her techniques and he wondered why she would go to such lenghts in order to have more power.