Dark Yugi and Mokuba Kaiba ' s Duel ( manga ) Dark Yugi and Mokuba Kaiba Dueled each other in the Duelist Kingdom tournament , in the " Yu - Gi - Oh ! " manga . Events . Prior . While Maximillion J . Pegasus tried taking over KaibaCorp , Mokuba swallowed an important key , so Pegasus had him kidnapped until the key could be retrieved . Mokuba was brought to Pegasus Castle on the Duelist Kingdom island . However he managed to escape the castle . Mokuba knew that Pegasus ' plan involved defeating Yugi Mutou in the finals of the Duelist Kingdom tournament , so Mokuba tried to eliminate Yugi from the tournament before that could happen . He stole a Deck and five Star Chip s form one of the participants and planned to use them to defeat Yugi . Dark Yugi , Katsuya Jonouchi and their friends saw the boy , whom Mokuba had stolen from , being restrained by Saruwatari and told he was to be sent off the island for losing all his Star Chips . The boy explained that the Star Chips had been stolen , but Saruwatari was unsympathetic . Jonouchi offered to catch the thief and asked that Saruwatari not remove the boy from the island until then . Jonouchi then added that he would keep half the Star Chips as a reward . While searching for the thief , Dark Yugi and Jonouchi noticed the boat that eliminated participants leaving the island on and among them was the boy whose Star Chips had been stolen , meaning they would not be able to return the Star Chips to him . Mokuba masked with a bandanna appeared before Dark Yugi and his friends . They recognized him as the thief , but did not immediately realize that he was Mokuba . Dark Yugi accepted Mokuba ' s Duel request , despite knowing he was the thief . The two of them wagered their five Star Chips . As they lay down the chips , Dark Yugi noticed that Mokuba did not have a Duel Glove , meaning he was not invited to the tournament . He wondered if the thief stole the Star Chips just to challenge him and started to become suspicious of something . Meanwhile , Dark Yugi ' s friends wondered why he accepted the Duel , when his opponent was clearly the thief . The Duel . 1st turn : Mokuba Mokuba Summoned " Man - Eating Plant " . 2nd turn : Dark Yugi Dark Yugi Summoned " Winged Dragon , Guardian of the Fortress " . " Winged Dragon , Guardian of the Fortress " attack ed and destroy ed " Man - Eating Plant " ( Mokuba : 2000 → 1400 Life Points ) . 3rd turn : Mokuba Mokuba Summoned " Crocodilus " . 4th turn : Dark Yugi Dark Yugi Summoned " Celtic Guardian " . " Celtic Guardian " attacked and destroyed " Crocodilus " ( Mokuba : 1400 → 1100 Life Points ) . Jonouchi thought that the thief was not very good and Anzu Mazaki agreed that he was no match for Dark Yugi . Dark Yugi advised Mokuba to give up , as the game is not so simple that it can be won with stolen cards . Mokuba knew he did not have a chance of winning , so tried to take Yugi ' s Star Chips instead . The Duel was not finished . Aftermath . Mokuba made a grab for the Star Chips , only managing to grab seven of the ten , but Dark Yugi caught him by the wrist , before he could escape . Dark Yugi then removed Mokuba ' s cap and bandanna , revealing his identity . When questioned about why he tried to steal Yugi ' s Star Chips , Mokuba told them that it was not for revenge . He told them about Pegasus ' plan to take over KaibaCorp , which required Pegasus to defeat Yugi in an official Duel . Mokuba had thought if he could make Yugi lose all his Star Chips , he would be disqualified before Pegasus could Duel him . Dark Yugi and his friends managed to convince Mokuba that they would help him and somehow find a way to beat Pegasus , whom Mokuba had heard was unbeatable . However when Mokuba tried returning the Star Chips , Saruwatari appeared and warned them exchanging Star Chips outside of a Duel was against the rules and could be punished with disqualification . So , Dark Yugi challenged Saruwatari to a Duel for the Star Chips , however Saruwatari himself did not play games , so he arranged for the Ventriloquist of the Dead to face Dark Yugi .