Red = Fire
Blue = Water
Green = Nature
Brown = Earth
Yellow = ?

No clue, but there's a flash game on his website using all these cards.

http://hokkyokutenban.web.fc2.com/flash_tohocomp.html

game2009 said:
Red = Fire
Blue = Water
Green = Wood
Brown = Earth
Yellow = Metal

First impressions were chinese elements, at least for me. Alternatively, swap Wood for Wind and Metal for Void and it's Japanese elements...

This is the first time I've seen a Japanese artist write Maribel's full name in Roman letters. Since there's no official romanization, they usuall don't.

And he wrote Kasen's title/hermit name/whatever it's called.

Kaguya looks rather annoyed that she's merely rare.

Is C Rare the same as Uncommon?

orin & futo act like rider V1 & V2

For some reason, I see Satori's pose as a variation of Dio Brando.

game2009 said:

Red = Fire
Blue = Water
Green = Nature
Brown = Earth
Yellow = ?

Probably electricity?

game2009 said:

Red = Fire
Blue = Water
Green = Nature
Brown = Earth
Yellow = ?

Yellow = Light