Mai assisted Emperor Pilaf in collecting the Dragon Balls with Shu. When a spy tracker spotted a glow in Skull Valley Shu and Mai came there only to see it was nothing but a bunch of Wolves. Shu and Mai were able to get away but Goku kicked down their plane causing them to crash. When they finally got back to Pilaf's Castle they were forced on another mission to get a dragon ball from Roshi the Turtle Hermit. When they got there Roshi already gave it to "a pretty girl on the beach". Roshi pushed there submarine into the ocean but put a hole causing them to sink to the bottom. Later during Goku and Bulma's time in the Diablo Desert, Shu and Mai attempted to blow up Oolong's House-Wagon to obtain the balls but end up failing when Shu gets the bomb stuck to his paw. When he manages to reset the bomb and get it on their house wagon Yamcha blows it up. Not knowing that Goku, Bulma and Oolong were gone, they both enter seconds before the bomb was set to go off and explodes with them in it. When they both get back Pilaf tortures them by shocking them for their failure.
When Goku and the others are on their way with six of the Dragon Balls, Mai tells Shu to attack them and take the balls. Mai then drives Shu with the dragon balls back to pilafs castle. Missing the ball Goku was carrying they gassed a room they were in to get the last Dragon Ball. Pilaf summons the dragon with the intention on ruling the world but Oolong interrupts and wishes for a pair of Panties.
Shu and Mai using her machine gun are sent to go after Oolong and the others. They captured all of them and put them in a special cell Pilaf designed to fry them. That night Goku turned into a Giant Ape from the Full Moon and smashed Pilaf's castle. Being in bed at the time Mai had to escape with Shu and Pilaf in a plane while still in her night gown. Using a missle to attack Goku causing him to fall Pilaf orders to go down. Realizing Goku isn't dead he grabs a tower and throws it at a plane causing them to crash. After Pilaf seeing the destruction of his castle he gives Mai and Shu guns and orders them to kill the rest of them but when Mai see's Pilaf running in the opposite direction she follows him along with Shu.