Sheppard, known in Japan as Samejima 「鮫島」, is the chancellor of Duel Academy in the first year.
Sheppard has all the traits of a beloved school headmaster, being both a strict disciplinarian and a child at heart. He has been known to stand up and cheer when watching a particularly exciting Duel, and covets a kiss from Ms. Dorothy enough to make it a prize for winning competitions.
In the second year, he left the job to Crowler. He leaves the school to invite Duelists to the Genex Tournament and to confront Zane. Sheppard meets Zane in a monastery on top of a mountain, where Zane seemingly trained as a Duelist when he was a child. Although Sheppard loses when Zane betrays his "Cyber End Dragon", he gives Zane a Genex Medallion and invites him to the tournament. Then he returns near the end of the second year to reclaim his job.
At the start of third year he is concerned that his best Duelist Jaden is still in the lowest rank dorm, hoping that Thelonious Viper whom he has just hired would push the boy into advancement. In the original Japanese version, he wanted Viper there to help Jaden continue to grow as a Duelist. No mention of getting him to be promoted was ever mentioned. At the end of the third season, during a meeting with Crowler, he decides he will begin a search for the remaining students who disappeared in the Abandoned Dorm.
In the fourth season, Jaden requests Sheppard to be allowed to leave immediately as he felt that all the major bad things at the school were because of him and he knew another threat was approaching. Sheppard was shocked at this, but he gets a phone call and asks Jaden to go to the island volcano, which Jaden reluctantly does. Later he and Ms. Dorothy would participate in the Duel Pair Tournament, but are beaten by Jaden and Alexis. Much later, he is beaten by Makoto Inotsume as part of the latter's plan to destroy the Cyber Art. After Nightshroud is defeated, Sheppard gives the graduating students their diplomas during the graduation ceremony.
Sheppard plays a Cyber Ogre Deck, a Cyber Art Deck with a strategy distinct from Zane's. Sheppard's Deck takes a more indirect approach, where he can turn his opponent's cards against them in both a physical and a metaphorical sense. Such cards include "Cyber Shadow Gardna" (a Trap Monster that can copy the ATK of the monster it is battling) and "Scrap Fusion" (which allows the user to Summon a Fusion Monster from their opponent's Fusion Deck). His most prominent cards are "Cyber Ogre" and its Fusion counterpart, "Cyber Ogre 2," both of which gain additional ATK when battling an opponent's monster.