Destroyer

The Destroyer (破滅屋) is a term used in Academy City's dark side to refer to an agent employed to become part of a team of other agents with the purpose of eliminating them after they have done their mission.

Principles
According to the destroyer that Tsuchimikado Motoharu corners after killing the people who were hired to kill his sister, Tsuchimikado Maika, he slips into large projects at the bottom level. He then intentionally causes trouble and secretly kill his colleagues. Those that want the project to succeed no matter what will want a greater guarantee of their success. They do not want any more problems and so the price of each individual soldier is driven up.

Agitate Halation Arc
He is part of the team hired to kill Tsuchimikado Maika as a reprisal for Tsuchimikado Motoharu's investigation of the Agitate Halation Project. He successfully kills all 9 of his colleagues, including Anjou Haruka, Kuromatsu Takao, and Imagawa Shiguma, former thugs working for the Spider Queen.

After a chase with the man, Motoharu manages to turn the tables on the man, and injuring him. Torturing him, he tells Motoharu his profession, to which he confirms that the deaths of his other teammates was not a cover up for the killing of his sister. Motoharu demands to know who behind all this is, to which he does not want to say for he fears them greater than the pain that Motoharu would undoubtedly do to him. As Motoharu tries to goad him through the use of a queer torture method, someone hits the man with the Sniper Bee. An assassin was sent to execute him, and Motoharu is forced into hiding. In excruciating pain, the man asks for reprieve, to which Motoharu is willing to help save his life in exchange for the information. The destroyer tells him of Yakumi Hisako, to which Motoharu gives him a bottle of toothpaste to use, the same one that he would use for his torture a while ago. Little did the man know that Motoharu was incapable of saving him, and gave him the toothpaste to consume as a means to give him a quick death.