* First appearance: Battle 286 * Type: Sei * Type: Satsujin Ken * Martial Arts: Iaido Sai Kagerou was a former member of Yami Armed Divison. He is a sword master who is able to attack and re-sheath his sword without appearing to move (getting the nickname Otokoeiaigiri and is also double-jointed, which gives him the ability to attack people behind him as if they were in front. The range of his Seikuken is enormous, easily including Kenichi who was standing several feet away from him, and extends even further than that, due to his enormous height and his sword, a Hitokiri Bouchou and Nodachi. His skills are so great that normal swords simply break down from his techniques, unable to withstand them, and he only feels a connection with Setsunamaru, the Hitogiri Bouchou he received from Shigure's father when Shigure was still an unnamed child, and a sword able to withstand his enormous techniques. He is even dangerous enough for Kushinada Mikumo, one of the One Shadow Nine Fists, who warned her disciple to read his "handbook" and is so powerful he almost managed to defeat Shigure. Sai is introduced as a master who is rather careless in his skills, as he cuts down one of his own allies reflexively and unconsciously while he meets with them to hunt for Kousaka Shigure. To compensate for this, he gives out instructions for dealing with him, amongst them to never point a sword at him, never insult him and to stay three meters away from him. He is quite courteous to both his allies and enemies, however he tends to become very excited in the middle of a fight After Shigure takes Setsunamaru from him, Sai loses confident in himself, reduced to cowering in his shack while birds built a nest in his hair. This extends to his honor as well, as he openly begged Shigure to give him back the sword without any regard for his dignity. Sai holds Setsunamaru dear to himself, likely because any other blade he uses quickly breaks from his power. His love for swords extends to a disinterest in women, whose faces he is never able to remember (he only remembers Kushinada Mikumo after recognizing her techniques). He will use other swords if deemed necessary but will feel no connection with the weapon, though when he does use the Akabanetou, he proclaims his realization of momentary love for the new sword and cries for Setsunamaru to forgive him for his infidelity.