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.

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.

History
At some points Wallenstein brought All-Goal to 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 tasked to Wallenstein, 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 but only after Wallenstein paid Nagi a ridiculous amount of money first. Under Wallenstein's tutelage Nagi had become a merciless assassin, killing any person Wallenstein had asked him to kill.

Akatsuki Strikes
Wallenstein was 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 had become 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 over power Shizuku during his fight with her, being able to nullify all of her attacks, do to his friction manipulation ability. However, Wallenstein is eventually defeated by Shizuku, by making her own body into water, and using the very air Wallenstein was breathing to drown him. Wallenstein survived the encounter and escaped through unknown means.

A Night of Massacre
During All-Goal's attack against Rebellion Wallenstein fought against All-Goal. He managed to cut down All-Goal's Deus Ex Machina and almost defeated him, only to be killed himself by Naseem Al-Salem.

Abilities
Friction Manipulation: Wallenstein has the ability to manipulate friction. With this ability he is able to nullify all physical attacks and steadily walk on ice without much problems.
 * Attack Nullification: By lowering, friction Wallenstein can nullify the power of any physical attack, making him basically invincible.
 * Attack Enhancement: By increasing friction, Wallenstein can 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 fight All-Goal who is a Desperado.

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 uses friction to increase the techniques power.