The mashin Ryuukotsuki is the primary antagonist of Getsu Fuuma Den. He has killed Fuuma's brothers, imprisoned their souls and conquered the world, and flooded it with demons and ghosts (fortunately not all of whom are quite so aggressive and violent). Fuuma must retrieve the fragments of the hadouken from three of Ryuukotsuki's top generals (Kyoukotsu Gyuugai, Ryuutoukibi, and Dokugan Dokuzu) in order to defeat him. Ryuukotsuki himself has three terrifying forms.
In Wai Wai World 2, he makes a decidedly less threatening and rather goofy appearance with a new body... looks like he's been working out at the gym!