Blade of the Immortal, Volume 7: Heart of Darkness

Having the members of the Mugai-Ryu be just as bad, if not worse, than some of the members of the Ittou-ryuu does make for an interesting way of setting up shades of grey in the story, particularly due to how utterly reprehensible some of the members if the Ittou-Ryuu have been in previous volumes in the series.