It never occurred to me that Nii might NOT be the major villain in the series, but that would certainly be a very interesting twist.

Indeed. I don't know, I kind of think he is though.

Koumyou is an enigma wrapped up in a mystery! Maybe Minekura will take pity on us and give us some more backstory for him. I find it intriguing that characters have said the Sanzo reminds them of a young Koumyou, because it makes me think Koumyou was not always the zen master, but far more volatile. It gives me hope for Sanzo too.