The 5th strongest of the Jyūshinshu and a well muscled unshaved man with dreaded locks and wears Hyōma En on his right hand in a saber hook fashion. He is called by Kurei as a lone wolf, but clearly by his revealing of his character during his fight with Recca, he was a close friend.
Part in story
Kai studied Hyōmon Ken under Meguri Kyōza, who also trained Mikagami. Through constantly comparing him to his senpai Mikagami by saying that Mikagami is "gold" and he is "stone", Meguri Kyōza instilled within Kai a sense of anger and revenge in order to show Mikagami how futile living his life only for revenge is. Kai battles against Mikagami in the final round of the tournament and manages to defeat him, fulfilling his desire to be the best Hyōmon Ken master and in order to avenge his broken pride. After telling Mikagami not to live a life of revenge the way he himself did and that it was Meguri Kyōza who killed Mifuyu, Kai stabs himself with the Hyōma En to feed its thirst and allows himself to fall into the pit below the arena.
In the anime, Kai is supposedly the first Hyōmon Ken successor, but is discarded soon after Meguri Kyōza noticed Mikagami's potential. He also says that Meguri Kyōza killed Mifuyu, but adds that Meguri Kyōza's reason for doing so is because he believed that revenge would drive Mikagami to train harder (he says nothing about Meguri Kyōza's motives in the manga). After his battle with Mikagami, he does not stab himself with the Hyōma En, but he still allows himself to fall into the pit.
An expert swordsman, Kai wields the weapon Hyōma En, which can manipulate ice and is the evil counterpart of Tokiya Mikagami's Ensui. In the manga, the Hyōma En has a mind of its own and constantly demands to be fed blood. He is able to take ice from moisture in the atmosphere using Hyōma En to continue to use his ice based attacks.
- Tsurara Mai (Dancing Icicles or Icicle Dance) - Not unlike the technique used with Ensui, it causes icicles to burst forth from the ground in a line toward the opponent. However, the icicles created by Hyōma En are much larger and have many smaller icicles on their surface.
- Hisame (Hail) - This technique consists of large chunks of ice being formed out of the moisture in the air and then are rained down on a target with tremendous force.
- Tou Kekkai (Ice Barrier) - This technique coats the weilders entire body with a thick shell of ice, protecting them from most attacks.