Kuzumi is always winning by dumb luck. :P He comes up with a few good strategies but it's so far-fetched how he can keep his top reputation for so long. I can imagine the day when everyone realises that he never had any magic from day one.
He won COZ he rescued Lucy. It's cool how he keeps coming out top and his rep is big, BUT he should seriously think about getting a proper magic card and doing cool magic so he can show off visually (Thats what I'd do)
