The most secrective more than even Noroi of the Jyushinshu and their wild card opposed to the trump card Joker being the 2nd strongest member yet was very uninvolved. He is a pale skinned white haired with frightening composed golden eyes wearing a completely white set of clothes. He never smiles throughout the whole series though he cries after his madogu is broken. He is unable to speak so he has his assistant Kirin read what he wants to say. In a way he is stronger than Kurei as he never lost his composure.
Part in Story
He does not appear until after the Ura Butō Satsujin, and by then he is serving under Mori Kōran as a member of the Ura Uruha. He wields the madōgu Kōkai Gyoku, which can erase anything at the expense of something of equal value belonging to its wielder. Because of his usage of Kōkai Gyōku, Rasen has lost his feelings, his mother, and his voice. He also loses his blood when he erases the flame balls produced by Nadare during his battle against Recca. Rasen mentions that he is searching for the moment wherein he would be erased as punishment for erasing his mother, but Recca defeats him and tells him to live on and to stop using the Kōkai Gyoku.
Rasen uses the Kōkai Gyoku one last time in an attempt to erase Kagerō's curse, and even though he managed to do so, the madōgu itself was destroyed because of the curse's power. The destruction of the madōgu caused Rasen to regain his feelings and his voice, and he is shown speaking in the last volume of the manga.
He is very agile and skilled in martial arts, but his most terrifying ability is his madogu Kōkai Gyoku. Kōkai Gyoku (光界玉 Light Ball?) - Known to be the most evil madōgu, it is an orb attached to the bottom of a telescoping baton, and is used by Rasen. It can erase anything from existence, even those that don't exist physically. However, it takes away something of equal value from its user. The orb has the symbol light (光 hikari?) written on it.