Duke Devlin Duke Devlin , known as Ryuji Otogi in the manga and Japanese version , is the creator of the game Dungeon Dice Monsters . Duke also owns the " Black Clown " game shop , which rivals Solomon Muto ' s Kame Game . In the manga , the Black Clown is owned by his father , " Mr . Clown . " Biography . Intro . In the anime , Duke invented Dungeon Dice Monsters and visited Maximillion Pegasus to demonstrate the game shortly before the Duelist Kingdom tournament . Duke was impressed by Pegasus ' skill at the game . Pegasus himself enjoyed the game and approved of the creation of Dungeon Dice Monsters , wanting to expand it further . Upon Pegasus ' request , Duke allowed him to make additions to the game , including adding the " Dark Magician " as a monster , and hacking into KaibaCorp ' s computer system . When Pegasus disappeared after being defeated by Yugi Muto in the Duelist Kingdom tournament , Duke blamed Yugi for his disappearance and believed that Yugi must have cheated to beat a gamer as good as Pegasus . He swore to get revenge on Yugi , whom he believed didn ' t deserve the title " King of Games . " After the Duelist Kingdom tournament , Duke opened the Black Clown ( a rival game shop to the Kame Game ) and transferred to Domino High School , the school that Yugi and his friends attend . He quickly became popular and impressed girls with a number of dice tricks . Jealous , Joey Wheeler challenged Duke to a game of " Duel Monsters " . They agreed to the stakes that if Joey won , Duke would close his shop , and if Duke won , Joey would be his slave for a week . Having been the runner - up in Duelist Kingdom , Joey was certain that he would win . However , not having his own Deck , Duke insisted that they play using cards straight from Booster Pack s . Joey agreed , and they each created a brand - new Deck . The Duel took place at the Black Clown . Duke televised the event in the hopes of humiliating Joey . Over the first few turns , Joey knocked chunks out of Duke ' s Life Points while leaving his own unscathed , but Duke managed to turn the Duel around and take out all of Joey ' s Life Points in one turn . In keeping his end of the bargain Joey became Duke ' s slave . Duke further embarrassed him by having him dress in a dog suit . Yami Yugi was disgusted by his treatment of Joey and challenged Duke to a Duel to release Joey . Duke was not interested in Dueling and challenged Yugi to a game of Dungeon Dice Monsters . If Yugi won , Joey would be free again , but if Duke won , Yugi was to swear on his grandfather ' s life to never play " Duel Monsters " again . Duke also televised his game with Yugi . Having not played Dungeon Dice Monsters before , Yugi struggled at first and Duke gained an early advantage . However , Yugi made a few comebacks and ultimately won using the " Dark Magician " that Pegasus had added . Duke then apologized to Yugi , having realized that Yugi was an honest game player and determined that he wouldn ' t have cheated against Pegasus . He began to worry that the televised game was going to be bad publicity as it made him look like a bad person . However , Yugi and his friends comforted Duke , assuring him that Dungeon Dice Monsters had the potential to become a great game . Soon after , Duke received word from Industrial Illusions in the form of an email stating that they would be helping produce Dungeon Dice Monsters , and had agreed to make the game global . Battle City . Duke appeared again during Seto Kaiba ' s Battle City tournament , where he saved Serenity Wheeler and Tristan Taylor from Rare Hunters , meeting Mai Valentine in the process . He watched the rest of the tournament along with the other characters . He is shown having a crush on Serenity , much to Tristan ' s disgust . Virtual World . Duke was trapped in Noah Kaiba ' s Virtual World along with the other participants aboard Seto Kaiba ' s Battle City Quarterfinals blimp . Along with Serenity and Tristan , Duke Dueled Nezbitt of The Big Five with the stakes being ownership of his body and the ability to return to the real world . At one point during the game , after drawing the Magic Card " Dice Dungeon " , Duke turned the arena into a Dice Monsters Dungeon , confidently telling Nezbitt , “ You don ’ t know me , but let ’ s just say I know a thing or two about dice . ” Battle City finals . Duke helps Joey when he collapses from his Duel with Yami Marik , and he cheers for Yugi during the Battle City finals . He parts with the group at the end of the finals , slipping Serenity his phone number , much to Tristan ' s anger . Waking the Dragons . During the Waking the Dragons arc , Duke was again reunited with the group after saving Rex Raptor and Weevil Underwood while they were lost in America . He helped them when they convinced him that they were friends of Yugi ' s . He assisted Yugi , Joey , and Kaiba against the Doma Organization and took part in a Duel with Rebecca Hawkins against Valon . For most of this Duel , his cards involved increasing the strength of Rebecca ' s dragon monsters . Despite summoning a powerful dragon , Valon beat them with his Armor monster s . Duke and Rebecca ' s souls were not taken after their loss as Valon never played the " The Seal of Orichalcos " during their Duel . However , he was unable to give the gang support later on because of being in another place during Yugi and Kaiba ' s Duel with Dartz . KC Grand Championship . Duke tagged along with Yugi and his friends during the KC Grand Championship . During the final episode , he said that he has a date with Serenity , and Tristan and Joey attack him for even saying so . Ceremonial Battle . During the " Dawn of the Duel " arc , Duke helped take care of Solomon Muto and contacted Yugi ' s friends and other important people , such as Maximillion Pegasus , about Yugi ' s absence . He accompanied Yugi to the Ceremonial Battle . He witnessed the Pharaoh ' s departure to the spirit world and the sealing away of the seven Millennium Items . Gaming items . Deck . Random cards . Duke ' s first Deck is made up of cards that he used in a Duel against Joey Wheeler , in which both Duelists agreed to open several booster packs of cards and simply use whatever they pulled from them . All the cards are from the " Thousand Eyes Bible " expansion of the " Yu - Gi - Oh ! Official Card Game " ( in the " TCG " , this set was merged with the " OCG " set " Pharaoh ' s Servant " and released as the set " Pharaoh ' s Servant " ) . Virtual World . In the Virtual World , Duke ' s Deck is based around " Dice " cards and utilizes several monsters he used during his Dungeon Dice Monsters match with Yugi , made mostly of Zombie s . Waking the Dragons . In the Waking the Dragons arc , Duke Duels one more time , although not much of this Deck is seen .