This happened to me last night. I carded the first grat I fought, which happened to be just past the "secret area" in the training centre, and I got a Shumi Card. Of course I continued to card every grat I fought, but they kept giving me grat cards after that.

Has this ever happened to anyone else? if so does anyone know the reason for it? Maybe its a glitch? I don't see how the programming in the game could be wrong in giving me that.