Actually there are 2 realy cool characters in the anime. 1 bad guy and 1 good guy. Almost none of their story is told yet. But basically the good guy is nicknamed "Kaze" (means wind) by the two main characters (who r children). The good guy seems pretty vital to the story however. Obviously cause he keeps geting resurrected and he is the source for the summons in the anime. Basically he has a metal tube covering his arm that "dissolves" and forms into a "demon gun". From here he chooses 3 bullets of diff colors and inserts them into the gun and fires aka summons a uhh Summon. So far this char is pretty cool. The other guy is pretty similar except he controls a sword thru telekenesis and uses flasks of liquid which r cut to cast spells. Cept he's not the main bad guy. More like a wandering mercenary (the main bad guy is a child).

So hopefully the game will be based on one of these 2 characters. And if it is may be a bit more than the "anime community" is expecting.