Gremlin

Not much is known about Gremlin yet, though it is clear that he is a member of Disaster, in which Kyoya Gaen is the leader. He appears to be a silent and serious person who doesn't talk much.

In episode 40, it is revealed that he is Baku's cousin, who in the past taught Baku how to build his first deck, as well as revealed to him the existence of the Darkness Dragon World. It is also revealed that he is the deck builder of the team, as shown when he build Davide Yamazaki's new deck.