She is voiced by Haruhi Terada in the Japanese version of the anime, and by Megan Hollingshead, Erica Schroeder and Alison Lester in the English version of the anime.
Mai is introduced as a selfish and arrogant woman who only participates to win wealth and fame. She is often very cynical about dueling, claiming that duelists only have themselves to trust and count on.
This cynicism leads her to cheer against Yugi Moto and Joey Wheeler during the first half of the season. After Yugi wins her star chips back from the Player Killer of Darkness, an eliminator who kidnapped and strongarmed her into dueling, she has a change of heart and begins to consider Yugi, Jonouchi, Anzu Mazaki, and Hiroto Honda as friends. She returns the favor by offering her extra star chips to Yugi following his defeat in his last duel with Kaiba. She later shows personal growth in character when she tries to knock Yugi out of his daze, and reveals she has learned from her last duel with Jonouchi about how a person can learn from their defeats than their victories.
Mai continues to follow Yugi and the others on their adventures in season two. During this season, she develops a strong bond with Jonouchi. Aside from giving him her entry card to qualify for the finals at Duelist Kingdom, she rescues his sister Shizuka from the danger of the Rare Hunters, and acts as her big sister, comforting her during Jonouchi’s duels. After Jonouchi woke up from his coma during his duel with Rishid, he tells everyone about his dream of all his friends helping him up. She asks if she was in that dream and he responds with a nervous “no”. She doesn’t take this well as she adopts an “every man for himself” attitude. During her duel with season two’s primary antagonist, Marik Ishtar, she ignores her friends’ cheers and continues proclaiming that she can duel on her own.
She reveals during the duel that she was alone as a child, living with wealthy parents who did not give her any attention. Upon obtaining a job on the cruise, Mai discovered Duel Monsters and became close with the "Harpie Lady" cards, regarding them as the closest things to friends she had. All of this displayed her true weakness: her fear of loneliness. Near the end of the duel, her individualist attitude is gone and she welcomes the help and support of her friends. As everyone parts ways following the end of the Battle City tournament, Joey confronts her about his true feelings as he fought for her during the tournament.
Waking the Dragons
In season four, Mai undergoes several personal struggles. Despite maintaining a winning streak in many tournaments, she fails to rank in the same class as Jonouchi, Kaiba, and Yugi, causing her to feel inadequate and alone. In addition to this, she starts having nightmares about Marik and her time in hell. This makes her susceptible and easy to lead astray, which allows Dartz to easily recruit her as one of his minions. As a result, Mai becomes cold and hard-hearted, wanting nothing but vengeance and power. Despite this, she is still plagued by the fear of losing.
After winning her last duel with Jonouchi, she not only realizes the error of her ways, but that she made a mistake in leaving Jonouchi for “a madman who promised me power” (according to her). Now filled with grief and anger over losing Jonouchi (as he was “the only one who ever cared about” her), Mai challenges Rafael to a duel in order to avenge Jonouchi (believing that Jonouchi would’ve done the same thing for her if their roles had been reversed and she had been in his shoes while he was the one who had won the duel while possessed by the Orichalcos). However, Rafael wins, and Mai loses her soul as a result.
Rafael later saves her life by pulling her unconscious body from the wreckage of the collapsing headquarters.
After Yugi, Kaiba and Jonouchi defeat Dartz, Mai’s soul is freed, alongside Valon’s and the others who were victim to the Orichalcos.
Mai spends the rest of the series out of the picture, reevaluating her life, and trying to rediscover her passion for dueling. In the English version, Mai claims she cannot face Jonouchi and the others until she can "face up" to what she's done. Mai leaves one of her "Harpie Lady" cards with Valon (in this case, "Cyber Harpie"); she also promises to return one day to both Joey and Valon. However, in the English version, Mai and Valon's relationship seems to end, and she does not say whether she will go back to Jonouchi.
She is on the invitation list to participate in the KC Grand Prix but only attends the final duel as a spectator to witness Yugi defeat Leonhart von Schroider.