Yu - Gi - Oh ! - Episode 151 " An Unexpected Enemy " is the 151st episode of the second series anime . It first aired in Japan on April 15 , 2003 , and aired in the United States on October 23 , 2004 . Summary . Kaiba , still reeling at the battle he ' s fought , decides to go see Pegasus despite an urgent mail from his company requesting his presence there . His plane is refueled in mid - flight . The driver of the limo which was going to drive Yugi Muto and his friends to Industrial Illusions has ditched them next to an abandoned oil stand . A group of bikers hired by Doma come and try to attack Yugi & co . However , Mai comes to the rescue with her bike and single - handily defeats all of them . The others don ' t realize in that moment , but she sports a Chaos Duel Disk , meaning that she ' s in league with Doma . Rafael and Valon are observing from a close distance . Valon looks rather annoyed with Mai ' s actions . The group flee in the limo , which breaks down , so they hitch - hike a ride towards the I2 HQ . Weevil Underwood and Rex Raptor wander aimlessly around the downtown streets of San Franciso . Just then , a man robs Weevil ' s wallet and runs off , only to be stopped by a dice hitting his face : Duke Devlin is here . The man drops the stolen wallet and runs off . Duke offers them a ride on his car and they make up a convincing tale to make it look they ' re worried about Yugi & co . because of the God Cards theft . They also head towards the I2 building . Yugi , Joey , and the gang arrive at Industrial Illusions , and the doors lock behind them . The gang is confronted by Mai Valentine . She reveals that she has joined Doma because of her loneliness and overwhelming drive to become the best Duelist . She reflects on her first assignment - - challenging Pegasus . Even the creator of Duel Monsters was not able to beat her , and although his soul is taken , she wants to prove her power elsewhere . Joey wants to free her from this influence , but he ' s the one that Mai wants to Duel first . He refuses , but she starts anyway and activates " The Seal of Orichalcos " , trapping him and determining that one of them will lose their soul . Even as she ends her first Turn , he still does not want to duel her , and he is at the brink of despair . Nothing he says is getting through to her , and fighting back would only mean that her soul could be captured . Featured Duels . Featured Duel # 1 : Mai Valentine vs . Maximillion Pegasus . The Duel is shown from an unspecified turn . Maximillion Pegasus has 100 Life Points . His field contains " Thousand - Eyes Restrict " ( who is equipped with Mai Valentine ' s " Harpie ' s Pet Dragon " ) ( 2000 / 2500 ) in Attack Position . Mai ' s Life Points are at 4000 , and her field has " The Seal of Orichalcos " in play . She controls 6 face - up " Harpie Ladies " ( 1800 / 1400 ) in Attack Position ( As " The Seal of Orichalcos " allows its controller to summon monsters in their Spell & Trap Card Zone ) . Neither player controls any face - down cards . Due to the effect of " Harpie ' s Pet Dragon " , " Thousand - Eyes Restrict " gains 300 ATK for each " Harpie Lady " on the field ( " Thousand - Eyes Restrict " : 2000 → 3800 / 2500 ) . Turn ? : Mai Mai draws " Harpie Lady Phoenix Formation " and subsequently activates it to destroy Pegasus ' s " Thousand - Eyes Restrict " and inflict its total ATK to Pegasus as damage ( Pegasus 100 → 0 ) . Featured Duel # 2 : Mai Valentine vs . Joey Wheeler - Part 1 . Turn 1 : Mai Mai draws " The Seal of Orichalcos " and subsequently activates it . From now on , all of Mai ' s Monsters will receive a + 500 ATK boost and the loser of this Duel will lose his / her soul . Mai then Normal Summons " Harpie Lady " ( 1300 → 1800 / 1400 ) in Attack Position . " Duel continues next episode . " Featured cards . The following cards appeared in this episode . Cards in italics debuted here .