Ironashi

He is the embodiment of Kyomu's Leader, Kokushou (黒将)'s black wave (黒い波動), whose death in a war against Canaima branch of Ángel in Venezuela years ago. It is the result of Shiva and the Hachishoujin trying to resurrect their leader. But the resurrection isn't completed yet, so he still doesn't have Kokushou's memories.

Kokushou's real identity is Hino Hakuya (日野 白矢), Aoba's father.