Nagi Arisuin/History

History
Nagi comes from a small town in Eurasia, staying in a church with a nun and several children including his friend Yuuri. One day, his younger friends were kidnapped by a group of mob ordered by the mayor which resulted in the death of his best friend Yuuri. In a rage, Nagi killed all the mobs emotionless but indirectly ended his friendships with his younger friends. While wandering alone, he ended up meeting Sir Wallenstein who offered Nagi a position in Rebellion which he accepted under the terms of being handed a large sum of money.

New Term and Rebellion
Nagi first appears inside his and Shizuku's room, alongside an angered Shizuku Kurogane over her issues with a certain princess who interrupted her and Ikki's moment together. Shizuku wonders if her love for her own brother was weird. Nagi then gives Shizuku some advice over this issue and decides to give Shizuku a makeover. Nagi is then invited by Shizuku, since her original plan was messed up by an intrusive Stella who invited herself along, wanting Nagi to be by her side, as she gains confidence when Nagi is around.Nagi and Shizuku then meet with Stella and Ikki outside the front gate of Hagun Academy, where he introduces himself to the latter, shocking them, as they assumed Nagi, being named Alice the entire time by Shizuku, was a girl. The group then heads to the mall, and visit restaurants while waiting for the movie to start. After finishing their lunch, Nagi follows Ikki to the bathroom, wanting to know Ikki a little bit better and starts a conversation with Ikki, realizing that Ikki is too used to being hurt to the point he can no longer hear the screaming of his soul in pain. Nagi sensing the surrounding then grabs Ikki and runs inside the bathroom as the sounds of shattering glass followed by guns and screams are heard.

Ikki contacts Kurono, who already knows the situation and tells them that Rebellion has hostages at the food court. Nagi uses his Shadow Walk ability to transports Ikki and himself to the top level of the mall staring at the hostages and finding Stella and Shikuzu among them. Nagi then stops an angered Ikki, who was about to go down, showing him the message, that said Shizuku was putting up a barrier. The conflict subsides as Nagi points out to Ikki that Stella had taken care of the rest. Nagi then gets the cops to arrest the members of Rebellion.

Debut Battle and Vow
Nagi is said to have won his first selection match against an E-Rank within 10 seconds, although it is unknown what method he used. He then goes to Ikki's match and cheers him on as he fights Kirihara.

Lorelei vs Raikiri
Two days after Ikki's victory over Kuraudo Kurashiki, Nagi interrupts, Ikki and Stella's intimate moment, after they were finally able to be completely alone for once. He tells them that Shizuku's tenth round opponent had been decided. She will face the student council president Tohka Todo, who was in the Top 4 of the last years Festival. Shizuku loses her match against Tohka, despite showing an amazing amount of talent and skill. Nagi later comforts Shizuku in her hospital room, saying that she did great and that it's okay to cry and show bitterness over losing.

Siege and End of Selection Battles
Nagi is mentioned in having to fight in his own selection battle and is unable to go to Ikki's match against Tohka. He is then announced one of Hagun's representatives in the 62nd Seven Stars Sword Art Festival, but does not appear at the ceremony as he has to convey the information of the participants for Hagun Academy, to an unknown source who is a part of an underground group called Akatsuki, as well as revealing himself to being one of their members.

Training Camp
Nagi participates in the training camp, bringing along Shizuku who is on medical staff. Nagi is later seen on the last night of the training camp stabbing Kagami in the back with his Darkness Hermit. When he contacts Hiraga in order to tell him that Kagami had discovered their schemes. He asked if he should kill her, but Hiraga finds that to be too complicated and insists on hiding her instead, as their plan of attack would happen tomorrow morning anyways.

After Nagi has hidden Kagami's body, he goes to his room where Shizuku is still awake reading a book. Nagi and Shizuku share a drink together and Shizuku points out that Nagi has finally opened up to someone, as he hadn't done so since arriving at Hagun Academy, much to Nagi's own surprise. This brief conversation makes Nagi realize that Shizuku has become his dear friend, and he wants to protect her.

Akatsuki Strikes
While on the bus back to the school, Nagi confesses to everyone that he is an assassin for Akatsuki Academy with the goal of stopping their movements and allowing the Akatsuki members to defeat them easily. The students at first turned on Nagi after this revelation, however, thanks to Shizuku pointing out the flaw in the very idea of an assassin pointing himself out before the plan is enacted, Ikki decided to trust him which allows the others to trust him as well.The students have arrived to a destroyed Hagun Academy, where they face off against Akatsuki Academy. Nagi is able to instead bind the students of Akatsuki with his ability, Shadow Bind. However he is soon stabbed multiple times in the back by Amane Shinomiya. It is then revealed that the real Akatsuki members were hiding as they knew of Nagi's betrayal thanks to Amane's ability. Nagi's unconscious body is then taken by Hiraga to Akatsuki Academy.

Nagi regains consciousness and is confronted by his master Wallenstein. Nagi tells Wallenstein that he betrayed him because he cared too much for Shizuku to allow her to be hurt. Wallenstein had become angered and begins to severely beat on Nagi. Shizuku then arrives and battles Wallenstein. Although she is unable to match him in power, Shizuku is able to defeat Wallenstein using her new technique and save Nagi's life.

After the Akatsuki scheme, it is revealed that Nagi had dropped out of the Seven Stars Sword Art Festival believing himself be a detriment to the team if he stayed in as a representative of Hagun Academy.

National Powerhouses
Nagi, Shizuku and Ikki decide to go out to eat and are invited by Yudai Moroboshi. They go to Yudai's family owned restaurant where they meet Kiriko Yakushi, one of the participants in the tournament. After lunch, Ikki separates himself from the group and Kiriko explains to Shizuku and Nagi why Ikki will have trouble overcoming Yudai.

First Round Matches
The next day, Nagi and Shizuku watch Ikki fighting and defeating last year's champion Yudai Morobashi. Next they watch Stella's victory against everyone else remaining in Block B. Nagi along with Ikki, Shizuku and Kiriko then meet Amane Shinomiya and learn Amane's ability to manipulate events to suit his needs which causes Kiriko to be forced to withdraw in her fight against Amane due to her patients entering critical conditions.

Later Nagi and Ikki are relaxing in the bathhouse, they meet Byakuya Jougasaki, who is the runner-up of the last year's tournment and Ikki's next opponent. Byakuya starts approaching Ikki and touching his body in amazement, with Nagi about to join, but Yudai shows up stopping Byakuya. Nagi and Ikki then leave, after Byakuya gives them cups of coffee.

Shopping Break
Nagi, along with Ikki, Stella, Shizuku, and the Akatsuki member Sara Bloodlily go shopping in the city. Nagi is asked by Ikki to find Sara some new clothes, as her current ones are impractical and could distract Ikki during their match. Nagi then takes Sara with him and instructs her on things like cosmetics and clothes. As they enter Nagi's Shadow Spot to try some makeup, Nagi questions about Sara's connections to Rebellion, with Sara telling him that she is in debt to Rebellion, as one of its Numbers, the Grand Professor, cured her of her illness. Later, Nagi shows Sara to the others, with her outfit being now even more revealing. Nagi though explains that Sara couldn't wear any more clothing, as her body is too weak, although her outfit won't at least be as impractical as before.

Nagi then leaves with Shizuku, who wants to prepare for her match against Amane. Shizuku tells Nagi about her plan to attack Amane, who is Shizuku's opponent in the quarter-finals, before the match. Nagi decides to help Shizuku because she is his friend.

Third Round Matches
Nagi and Shizuku attack Amane, while he is in the waiting room. After Amane survives Shizuku's attack, Nagi tries to use his Shadow Bind on Amane, but the lights of the room, temporarily go out, negating Nagi's shadow abilities. Amane then pierces Nagi with multiple swords taking him out of the fight. Amane also defeats Shizuku. Both Nagi and Shizuku survive and are later healed.

Preparation for the Final Match
Nagi is seen battling Ikki in a mock battle, helping him train for the upcoming final match of the tournament. Though Nagi puts up a good fight, Ikki takes the upper hand in the battle, being more skilled than Nagi. The fight is however interrupted when other students, including Tohka and Yudai, arrive to help Ikki train.

The End of the Festival
After watching Ikki's victory against Stella in tournament's final match, Nagi later accompanies Shizuku to Ikki and Stella's hospital room the next morning. Nagi quickly realizes that Ikki and Stella had sex last night, and when Shizuku realizes this she attacks Stella. He is later present during the crowning of Ikki as the new Seven Stars Sword King.

Post-Festival Meeting
Nagi participates in the party held after the tournament is over. He tells Shizuku that he plans to visit the grave of his childhood friend in his hometown.