Mikey once lived in Satellite, where he and his family were deprived of a lot of life's luxuries. After the Dark Signers were defeated and Satellite was reconnected with New Domino City, the family moved to New Domino and began a normal life.
Using false documents, Piero conned his family into owing him money. As they were unable to pay in time, he repossessed their belongings.
Mikey followed his older brother, Marco, to the Duel Statue where Marco left his cards and prayed for the Duel Goddess to use them to defeat Piero. Mikey tried talking him out of it, as he would be unable to Duel himself if he went through with this. Believing that to be the case either way, Marco still left the cards.