He is a member of Yami's weapon group and is a sword master, able to attack and re-sheath his sword without appearing to move (getting the nickname supersonic) and is also double jointed which gives him the ability to attack people behind him as if they were in front. He owns a sword, Setsunamaru, made by Shigure's father, which he received while she was still a child. When she noticed that he had sliced a bird (which she refers to as "my first friend" in half (recalling that she was unable to see the movement) she instantly attacked him; but before she made contact he had already dodged the attack. Were it not for her father's insistence that Sai leave immediately, he would have killed her. Before he left he told her that she had to wait a few years for what awaited her next, an event which she describes as her "trauma". When he works with other people he has them stay 3 meters away from him and tells them to never approach him from behind because he would instantaneously attack them with enough force to almost kill them; all of this is unintentional and he doesn't even notice. He apologizes to one of the fellow head-hunters, who was the recipient of a reflexive sword wound. At the beginning of his duel with Shigure, Kenichi is able to see the full extent of Kagerou's Seikuken. The range of his Seikuken is enormous, easily including Kenichi who was standing several feet away from him, and that his Seikuken extends even further than that.
After his defeat, Shigure takes his sword, Setsunamaru, from his possession.