Cat M (Maomi Yuuki) is one of the two main villainesses of "The Lost Ship in the Sky". She is the member of an evil foreign mercenary group undercover as one of the waitresses abroad the Bell 3 Airship owned by the Suzuki Corperation, as well as the site of display for "Lady Sky", the target of Kuroba Kaito (Kaito Kid).
Cat M was first introduced to the guests and police abroad the ship as one of the waiter/waitresses. She was the one who had Takamichi Fujioka and the other waitress, both infected by an unknown virus planted by the terrorist group inside the ship's smoking room, transported to the infirmary under the order of Inspector Ginzo Nakamori and Jirokichi Suzuki. Cat M's villainous reveal came shortly after her male cohorts hijacked the airship, revealing herself to be the mole among the passengers. The villainess revealed her hidden gun and slapped Ai Haibara after witnessed the girl's attempt to inform her friends the Detective boy of the situation through her Detective Badge. Shortly after, Cat M then watched as her leader threw Conan Edogawa off the ship due to the boy having previously disabled all the planted bomb, however, Conan was saved by Kaito and his hanglider after tearing off his waiter disguise.
Later that evening, after Conan and Kaito returned to the ship and incapacitated majority of her cohorts, the evil Cat M was ambushed by Kogoro Mouri when she rushed in to the cabin where the passengers had been confined. The villainess then received a painful Judo Throw from Kogoro, knocking her out instantly. She and her cohorts were then restrained, ready to be handed to the Police once the ship had landed. At this time, Conan Edogawa and the Police later discovered that Cat M and her cohorts was actually hired by Takamichi himself, who was also the mastermind behind this complicated crime. Prior to the story, the villainess and her group had hijacked a Laboratory and pretended to steal dangerous virus. In truth, no virus was stolen, and the supposed infected that happened on the ship was infact Lacque Allergy, in which Cat M had sprayed in the smoking room in advance, intending to confine the passengers and to create the virus fear among the people in Japan. Once the people of Osaka had evacauated, the other half of the mercenary would then robbed all the priceless Buddha statues while disguising as policemen. After escaping from the airship, the group would then denote the bombs and silence all the witnesses.
Unexpectedly, Cat M and her cohorts were betrayed by Takamichi and his direct underlings: Kasumi Nishitani the reporter and Junpei Nishimoto the cameraman. As Conan confronted Takamichi atop the airship, Kasumi and Junpei revealed to Cat M and her cohorts that the three had changed their target from Buddha Status to Lady Sky and decided to kill them off along with the other passengers. Fortunately, Conan Edogawa managed to knock Takamichi off the airship into the river and changed airship's direction to upward to avoid crashing, knocking Kasumi and Junpei into the wall due to gravity, with Cat M and her cohorts along with the other passengers being saved ironically due to their restrain. Cat M and her cohorts along with Kasumi, Junpei, and Takamichi were presumbly arrested (offscreen) afterward.