Do you actually have permission to use those character sprites? They look like they're ripped from a game.
All assets used in this particular game (BGs, Character sprites, sounds, music etc.) are distributed as 'free to use' - some with special circumstances attached. Those sprites are in fact from a card game (I'm not sure if this particular one is still active or not but); you can check out their website and terms of conditions here: http://www.jewel-s.jp/download/
I placed a full list of the assets I used here: http://kunikai.tumblr.com/post/129284768877/tyrano...; which is also seen at the ending credits of this game.
Hope that cleared it up ^^; sorry if it wasn't clear.