Michael Kaiba is a duelist and the secret son of Seto Kaiba, which he didn't find out until Kaiba's death. In addition to owning all of Kaiba's Blue-Eyes cards, he also owns three copies of Rabidragon.
At an unknown point in time, Kaiba and an unknown woman had a son (it is unknown if they were married or not) after his mom died, he lived his life on the street, gaining money by dueling. His timeline is that of ZEXAL, but he despised Xyz Monsters. When he turned 15, he was called to the Kaiba mansion where a dying Seto Kaiba revealed to Michael that he is Michael's father. Seto then told Michael to get the Blue-Eyes White Dragons from his secret area underneath the library. There, Michael dueled a Kaibabot that mistook Michael for an intruder. Michael defeated the robot and gained the Blue-Eyes White Dragons and the Blue-Eyes Ultimate Dragon from it. He then went home to Heartland City where he took over became Vice President of KaibiCorp under his uncle Mokuba as president. During an unknown period, Heartland announced a tournament similar to Battle City, in which the victor can choose to take one of their opponent's cards. Michael dueled Yuma and won, thus taking Number 17: Leviathan Dragon, Yuma begged for the card back but Michael swore if Yuma met him in the finals, Yuma may be able to take Leviathan Dragon back. During the finals, Michael dueled against Kite and purposely lost so as to not fulfill his promise to Yuma. Shortly afterwards, Heartland disappeared, allowing KaibaCorp to buy the city.
Negative Number arcEdit
Years later, Yuma, now old enough to Turbo Duel, snuck into the Kaiba Heartland mansion and challenged Michael to a duel for Leviathan Dragon back. Yuma was winning until Michael pulled out Dark End Dragon which used its effect to send Utopia straight to the Graveyard, allowing Leviathan Dragon and Dark End to attack Yuma directly, but the duel was interupted by visions of the Negative Numbers, causing both Yuma and Michael to crash. Both unurt and their runners only had minor scratches, they decided to part ways for now and think about what they saw, then duel again for the fate of Leviathan Dragon later. One day while he was out riding, Michael was ambushed by Markov, and challenged to a duel, Michael accepted. During the duel, Markov managed to summon his Negative Number, which Michael destroyed with his Galaxy-Eyes Photon Dragon Scrap Dragon and defeated Markov. Michael then told Yuma and Kite about the Negative Numbers, Hart explained that the Negative Numbers must be responsible for causing so many good people to begin acting evil, a worse influence than the "Numbers" ever were.
Michael uses a Dragon deck, much like his father. His signature cards are Blue-Eyes WHite Dragon, Rabidragon, and Scrap Dragon until he gave up the Rabidragons and put them in a different deck, which granted him the power to summon the Azure-Eyes SIlver Dragon.