 If you liked
Riki-Oh
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 ...then you might like
Chijou Saikyou no Otoko Ryuu
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Both of these series are absolutely batshit insane martial arts manga that involve overpowered main characters, ultra violence, and incorporate religious elements into the story. While Ryuu's plot is considerably more unhinged, both of these manga are just a series of ridiculous circumstances and only get weirder as they go on.