Eiku Shizuma(Jpn. - 閑馬永空 - "Shizuma Eiku") was an early member of the Itto-ryu and the first immortal antagonist in Blade of the Immortal.
Shizuma was given the kessen-chu much like Manji. However unlike the recently immortal Manji, Shizuma had been immortal for nearly two-hundred years learning of powerful poison that prevent them from regenerating the wounds in the body. He covered both of his weapons in this poison and use to fight other immortals. He was shown with aspiration for taking over the world finding Manji a possible ally but was quite disappointed when this was not the case. As with other immortals Shizuma lack the fighting style of normal human not even flinching at pain or trying to doge attacks his very immortality becomes his weakness, one that Manji fear has weaken his swordmanship. At the end Shizuma was killed by decapitation and the same worm-poison which slowly took effect showing just how strong the kessen-chu could be. While the poison he use is never given a proper name other than 'Wormkiller' its however later use by Fujiaki Kasori to try to kill Manji.