The striped sweater Duelist was an unnamed character in the manga and second series anime.

Bumblebee manga

The striped sweater Duelist in the manga.

He was a participant in the Duelist Kingdom tournament, but lost to Mai Valentine at an early stage, as she defeated him using her "aroma tactics". After Mai takes away his Star Chips, he shouts out that she'd been using some sort of psychic powers, mocked by Mai he went off weeping.
