Chatarou Buke

A short and afro-haired boy who is a childhood friend of Katta's. While his dueling skills are considerable when Katta was still young, in Katta's first timeskip in DMVS, he was overly attracted to idols and forgot how to duel. He has never won a duel throughout the visible part of the anime since then.

(Source: Duel Masters Wiki)