- Mio to Shuu on the rooftop on September 18.(src)
November 15, 1993
Mio's hair is tied up in two buns with thin white ribbons, and wears two hairclips, one a yellow crescent moon and the other three pearls. The ends of her hair are a little curled.
Her hairstyle bears slight resemblance with Rin Tohsaka from the anime Fate/Stay Night, only the black ribbon twintails switched with white ribbon buns.
Mio is a diligent and model class representative of class 2A. Knowing the soft and frail side of Shione, which makes her worries to no end, Mio acts towards her like a protective mother, always do everything she can to make her happy, even if she has to neglect her own feelings. However, Shione is also the main reason behind Mio's attitude towards people on some occasions. While she tries to be polite and diplomatic to other students, Mio is extremely aggressive when it comes to dealing with Shuu Amami due to her friend's feelings for him. She gradually shows her warm side to him over the course of the story, as she realizes he is not so bad of a person.
Mio is the class representative of class 2A and a close friend of Shione. She is not in good term with Shuu because his rejection to Shione's confession. Like Shuu, she is also a modern mage and she hid that fact even from her best friend. It's revealed that her father was Kanji Amami's student, who was Shuu's grandfather.
A Friend in Need
On September 15 night, Mio took a walk as she was unable to sleep. She called Shione to confirm her success with her confession, but found out that Shione was rejected instead. Mio was disturbed by this fact. She told Shione to never give up, that she still had a chance, and added that she would help her.
The next day, Mio came to the school and saw that despite what she told Shione last night, Shuu completely ignored Shione and Shione was too embarrassed to even talk to him, which got on Mio's nerves. She called them outside class to talk. As Shuu asked her what she wanted, she angrily asked why he didn't pay attention to Shione, who was trying to get a chance to talk to him. Shuu said that it was not her business, but Mio replied that Shione's business was also her business. Before she could say anything, Shione said that being able to talk to Shuu normally made her happy enough. After that, Kaori and Tadashi spotted Shuu and came to talk to him, leaving Mio unable to say anything else.
On September 17, she encountered Shiori Momono on the bridge. Realizing that Shiori was a mage from Index, which had the reputation of using ruthless methods to achieve its goal, she used her magic, attempting to repel Shiori out of the city. However, Mio was almost killed if it was not for Shuu's intervention.
A few hours later, Mio woke up and found herself inside Shuu's house. Thinking that he was trying to do something to her, she attempted to hack into his magic system, but failed. She then desperately tried to escape from him, but he held her back easily, telling her to calm down. After a while, she calmed down and told Shuu that he should keep what he saw that night a secret. Shuu asked her whom she learned modern magic from. Being suspicious of him, Mio said that it wasn't his business and countered why should he care. Shuu said that he asked because he thought she was really good at magic, making Mio blush. Having nothing else to say, Mio went home, thanking Shuu for saving her before leaving.
On September 18, Shiori transferred into the Academy and shocked both Shuu and Mio. They later met on the rooftop and discussed as to what an apostle of Index was scheming in Ayamegaoka. When Mio was about to go away, Shuu stopped her. Unexpectedly, Shione came to the rooftop right at that moment and thought that they were kissing. She tearfully ran away and Mio chased after her to explain. Mio found her at the riverbank and seemingly managed to explained the situation. After a while, when Shuu got there, Shione apologized to him.
Mio saw them having a friendly conversation and used that chance to force Shuu to become Shione's friend. Her intention was obviously to get them closer to each other so Shuu might develop feelings for Shione one day. However, unaware of that plan, Shione thought that she wanted three of them to become friends. Mio could not reject her best friend's request, so she reluctantly became friends with Shuu. She still didn't like him, but her attitude towards him changed over the course of the story thanks to Shione's affection and more time with Shuu.
On September 20, while going out with Shuu and Shione (as they had become friends a few days ago), the group encountered Tadashi and Kaori, who were showing Shiori around the town. Shuu and Mio tried to act calm like nothing happened between them before, but the awkward atmosphere prolonged. When they got inside Ayanas, the tension increased even further as Shuu spotted Kaori's doppelganger watching the group from afar. Shuu was at a dilemma because should a battle of three sides occur at that moment, he would not be able to get Tadashi, Kaori and Shione out of there in time. However, upon seeing Shuu with a serious face, Tadashi made a stupid joke and broke the tension as if the Doppelganger wasn't there at all.
In the afternoon, after Kaori, Tadashi and Shione had gone home, seeing Shiori with Shuu, Mio attacked Shiori with a spell called Wind Edge; Shiori managed to dodge it. Mio said that they should finish everything once and for all, refusing to listen to what Shiori had to say; however, Shuu managed to persuade her to calm down.
As the tension was gone, the three went to the park to talk. Shiori said that she was sent by Index to Ayamegaoka to keep watch and report the situation to headquarters; her encounter with modern magi such as Mio and Shuu was something she did not anticipate. She also said that she would not report the existence of modern magi in Ayamegaoka to Index, as she did not know what they would do with the information; however, when Shuu asked what exactly did Index want her to report on, she refused to talk and only gave them a heavily classified explanation in which the only thing they shared in common was the involvement of the Doppelganger. After listening to Shiori, Shuu deemed that Shiori was no threat to him and decided to co-operate with her－or rather, to become friends－to solve the mystery of the Doppelganger. Although reluctantly, Mio also agreed, as she wanted to protect the town as well as Shione.
The Doppelganger Attacks
On October 2, she received a distress call from Shuu that the doppelganger had appeared in the Academy and he wanted her to make sure that Kaori and Tadashi were safe. Mio then called Kaori and Tadashi to the riverside and stayed there with Shiori to wait for Shuu. Kaori demanded Shuu to tell her what was happening. While Mio was reluctant, Shuu revealed their identities as magicians to Kaori and Tadashi. At first they didn't believe him. However, Mio then remembered that Shione was alone at Ayanas and Shuu told Shiori to get there. Shiori teleported to Ayanas before Tadashi and Kaori's very eyes, leaving them no choice but to believe Shuu.
When Mio got to Ayanas, she was astonished to see the two Shione. Shuu managed to deduced who was the real one, forcing the doppelganger to reveal its true form. As the gang was about to capture it, the Doppelganger activated a green Specialized Bounded Field which prohibited the use of magic, rendering Mio and Shu useless. Shiori, whose body was running on magical energy, was affected most badly; she couldn't even move or say anything. With all the threats neutralized, the Doppelganger kidnapped Shione and ran away.
Having no options left, Mio agreed to lend Shuu some her her life energy to strengthen his physical power and defeat the Doppelganger. Due to Shuu being the only one who could fight without using spells at the time, Mio had to stay behind. After the battle, Shione came back with Shuu, who brought the Doppelganger's core and used that to enable Shiori's movement. They set out to find the exit out of the barrier, and successfully got out.
Battle of the Mirror Field
On October 22, Mio came with Shuu to the park to fight with Kanae Kuroshida. Their plan was to buy Shuu enough time to complete Exhaustive Search on Kanae's abilities. However, even with the help of Shiori, they were still at a disadvantage. As the battle was about to be set, Mio challenged Kanae to a one on one battle and entrusted Shuu with defeating Kanae once she did her job. Kanae accepted her challenge and cast a barrage of lightning on Mio, who, in turn, used Worlds Collide as a means of defense. Mio was almost killed when Kanae crushed her internal organs with modern magic. However, she managed to survive and bought Shuu enough time to execute his plan.
Thanks to Mio's help, Kanae was defeated in the end.
On November 6, Mio was asked to Shuu's house, to which she agreed. When she arrived, she joked and asked if he wanted to talk seriously, or just wanted to flirt around. Shuu responded by asking her to study modern magic with him. Mio refused, saying that she would only slow him down, and she would be happy if he could just accept Shione's feelings. However, Shuu insisted, saying that he had decided to continue his path with her as his partner. Mio was struck with fear as she finally understood what he was implying. Seeing the look on Mio's face, Shuu continued and confessed his feelings, which rendered her speechless. He asked if she hated him, to which she said that she did not know. Then he asked if she liked him, and Mio finally replied: "I don't hate you." Shuu held her hands and kissed her. Mio received the kiss, but then pushed him away immediately. She began to cry, as even though her desire to protect Shione was strong, she could not deny her feelings for Shuu. As her mind was still in turmoil, Shuu suggested another option: going out with both Mio and Shione. Mio made an 'unbelievable' expression, and blushed at the outrageous idea.
Some time later, Mio actually took on the suggestion. Shuu, Mio and Shione went on a date (Shione did not know that it was a date). Shione commented that Mio was surprisingly early, then asked why she was so fond of going out recently. Mio tried to feint innocence, but her expression gave her away, embarrassing her. Shuu said that he felt hurt seeing the two girls so intimate. Shione then said that she and Mio were more than just friends, which stunned both Shuu and Mio (they thought that she was implying a yuri-like relationship). Mio blushed and asked what Shione was trying to say, and the latter answered that she was going to say 'best friends', again surprised others.
- Modern magic expert: Mio's father is the student of Shuu's grandfather, who is the creator of modern magic. She inherits her father's magic using style through reading his old textbook. Even more than that, Mio appears to be quite good at modern magic as Shuu observed. It was because she laid down a network of familiar in critical points in the city which Shuu failed to detect. She is also able to control elemental spells well, which Shuu claimed to be difficult. However, due to her family not being an experienced blood line of magus, she has very limited knowledge about the magical world such as the details on Index or its arch-nemesis Thule.
Shione Azuma: Shione is Mio's best friend, and Mio cares deeply for her, and is very protective toward her. The reason why she wanted helping Shiori was to protect Ayamegaoka, as well as Shione. She tried making her and Shuu together, and she had been angered when he rejected her. Even if Mio developped feelings for Shuu, her friendship with Shione is more important, wanting Shione's happiness rather than confessing her own feelings. It's implied, in Mio's ending, that Shione and Mio are more than just friends, but best friends, according to Shione (even if Shuu and Mio thought it was a love relationships at the beginning).
Shiori Momono: She fought against her in the beginning, but was saved by Shuu. Later, when Shiori became a student in her class, she mistrusted her, but when Shiori revealed the truth, she agreed for helping her and the two of them became friends later.
Shuu Amami: The two of them didn't get along well in the beginning, since Shuu rejected Shione, and was very angered against him. Later, their relationships improved thanks to the events and Shione, who wanted three of all them being friends, and Mio fell in love with him, but she couldn't admit it, and acted tsundere toward Shuu. At her ending, they kissed and Shuu decided to go out with both Mio and Shione.
- She makes a bit the "Misuzu" in replacement in this arc, as being red-haired and a tsundere toward the hero.