Mai was unhappy that contestants of the Duelist Kingdom had to sleep on the floor in a common area on the ship. She noticed Rex Raptor had been given a room because he was a finalist in the Japanese National Duel Monsters Championship and came up with a plan to use him to get a room. Rex allowed Mai to use his room. Mai acted all happy and flirtatious to him and went along.
Inside Rex's room, Mai said that she likes men who were stronger than her and challenged him to a Duel. Mai said that if Rex won, she would do whatever he wanted all night long. (In the English anime, she said that she would give him a kiss.) And if Mai won, she would get the room all to herself.
Mai got Rex to shuffle her cards and then she asked him to look through them as she named each card from top down without looking. Using her Aroma Tactics, she correctly named the cards, "Shadow of Eyes", "Harpie Lady", "Elegant Egotist", and "Cyber Shield". Rex thought it was impossible, but Mai claimed to always know her cards and be able to draw whatever she wanted. Rex still accepted the Duel and was defeated. Afterwards Mai kicked him out of the room.
When they got to the island, Rex was still angry over his loss to Mai and tried challenging her to another Duel. She was not interested in facing him again, but decided to let him Duel her if he could first defeat Joey Wheeler.
- Yu-Gi-Oh! episode 3: "Journey to the Duelist Kingdom"