Kyofuga (恐怖牙, Horror Fang) is one of the new generation of Ninja blades utilized by the current Seven Ninja Swordsmen of the Mist. Kyofuga does not take on the appearance of a standard katana, but instead it looks fairly menacing as it is a large scythe with an elongated handle that forms into a skeleton with spiky vines wrapped around the cranium and its beautifully designed blade sticking from the back of its body.
Kyofuga's true strength is strange for a sword as it allows Yun to enchant an area around him and his opponents. This area reaches a two mile radius in any direction once activated, with Yun as its focal point. Once inside he gains the ability to produce a blue colored flame that he can manipulate as an extension of himself. After an object has been struck and burned, they will be subjected to the rules that Yun has set in place. He is capable of forcing the opponent to submit to as many rules as he chooses without having to remove the previous ones unless they conflict with one another. Each time the opponent is struck by the blue flames they become less able to resist Yun's rules and ultimately will become his unwilling slave, even if Kyofuga is broken. For those who insist on resisting or breaking Kyofuga's rules, there is a punishment that Yun has set in place in order to slowly break down the mind of his opponents.