Wallenstein

Wallenstein, also known as the "One Armed Swordsman", was one of the Numbers for the terrorist organization Rebellion and the former mentor of Nagi Arisuin.

Appearance
Wallenstein was a middle-aged man. He had short hair and scars over one of his eyes. He usually wore a black robe.

Personality
A very hardened individual, Wallenstein believed that there was no love in the world and that anyone who thought there was such was foolish.

Wallenstein has shown to be a very cruel individual wanting to punish Nagi before killing him, by killing the very person Nagi has taken to as his sister. Wallenstein was also a sociopath as he took lives without much remorse or care. Wallenstein also seemed to have an important position in Rebellion, having trained many of it's assassins.

History
At some point Wallenstein brought All-Goal to join Rebellion, in order to help their cause.

Wallenstein was hired by a mayor of the town Nagi was leaving at as an orphan. After Nagi killed all the gang members, for killing his friend Yuuri and capturing other orphans, who Wallenstein was tasked to kill. He then introduces himself to Nagi and gives Nagi a gift, the severed head of the mayor to him. Wallenstein then persuades Nagi to join him and his organization, Rebellion, but only after Wallenstein paid Nagi a ridiculous amount of money first. Under Wallenstein's tutelage Nagi becomes a merciless assassin, killing any person Wallenstein had asked him to kill.

Training Camp and Scheme
Wallenstein talks with Nagi on the phone, during the training camp, after Nagi has called Reisen Hiraga. He asks if Nagi is ready for his role to betray the Hagun students that he has pretended to be a friend of for months. Nagi answers positively, which pleases Wallenstein, who believes Nagi to be the greatest student he has had.

Akatsuki Strikes
Wallenstein is first formally seen at Akatsuki academy, when he began to interrogate on the reasons why Nagi would betray him. After learning Nagi's reasoning was because he cared about someone, Wallenstein became angered and then decided to punish Nagi before killing him, by killing the very person he cared for the most, Shizuku, who had just arrived.

Wallenstein was able to overpower Shizuku during his fight with her, being able to nullify all of her attacks, due to his friction manipulation ability. Wallenstein seemingly kills Shizuku, but Shizuku manages to survive by turning her own body into vapor with Aoiro Rinne. Wallenstein is defeated by Shizuku, the very air Wallenstein was breathing to drown him. Wallenstein survived the encounter and escaped through unknown means, returning to Rebellion's headquarters.

A Night of Massacre
During All-Goal's attack against Rebellion Wallenstein encounters All-Goal, intending on killing All-Goal. All-Goal though is not intimidated by him, mocking Wallenstein for losing to a B-Rank student knight. Wallenstein however, manages to cut down All-Goal's Deus Ex Machina and almost defeated him, only to be killed himself by Naseem Al-Salem. It's though implied that All-Goal didn't take the fight seriously, having only been playing around.

Abilities
Friction Manipulation: Wallenstein had the ability to manipulate friction. With this ability he was able to nullify all physical attacks and steadily walk on ice without much problems.
 * Attack Nullification: By lowering, friction Wallenstein could nullify the power of any physical attack, making him basically invincible.
 * Attack Enhancement: By increasing friction, Wallenstein could greatly increase the power of his attacks.

Master Swordsmanship: Wallenstein was regarded as one of the strongest swordsmen in Rebellion, despite him only having one arm. Nagi Arisuin also regarded his skills highly. He was even able to engage All-Goal who is a Desperado.

Expert Assassin: Wallenstein was a skilled assassin, having taught Nagi and being one of Rebellion's strongest members.

Device
Unnamed Sword: Wallenstein was shown to have a sword as a Device, which he could over power many foes with, without much effort.
 * Bergschneiden (山斬り, lit. Mountain Cutter): A deadly cutting attack used by Wallenstein. It was strong enough to cut through All-Goal's Deus Ex Machina and the mountain behind it. Wallenstein most likely used friction to increase the techniques power.