Ai is the secret real first name of the leader of the Sly Girls.
Soon after the mind-rain, Yokohama decides to base its currency on face-rank and merits. Ai isn't too thrilled about either, and soon founds the Sly Girls as a way to fight the system. She doesn't seem to care who joins her clique as long as the girl doesn't want to be famous and keeps their tricks secret.
Her goal is to be the most anonymous person in the entire city, despite organizing infamous tricks such as mag-lev surfing. To accomplish this, she changes her nickname often.
- Main article: Extras (book)
Ai, going by the name Jai, holds a meeting in the underground storm drains of the city. When the only famous Sly Girl, hoverball star Eden Maru, is trailed by Aya Fuse, Ai organizes a quick ambush of the unlucky would-be kicker. She locks down the girl's hovercam and knocks her off her board and into the underground lake, explaining that she doesn't like kickers.
Aya thinks fast and claims that she isn't a kicker, she just wants to join them. Although suspicious that Aya is lying, Jai is impressed that a fifteen-year-old had the guts to follow them at all and decides to give the girl a chance. She lets Aya make a choice: either take the hovercam and get out of her sight, or allow her to drop it to the bottom of the lake and come mag-lev surfing with them. Aya chooses to let her beloved hovercam, Moggle, sink to the lakebed. But before Jai lets her join them, she wants to see if Aya is lying about being a kicker first and sends the girl home, promising that they'll be in touch.
The next night, Jai sees potential in Aya despite seeing that she's kicked stories and decides to invite her to surf with them. She explains that if anyone in front of her waves a yellow light, it means duck. If the light is red, it means a tunnel is coming and she must lie flat on the train. The other Girls are uneasy that Jai is allowing a fifteen-year-old kicker to join them, but Jai defends her decision.
This time though, the mag-lev unexpectedly stops inside the tunnel. Aya and another Sly Girl, Miki, witness strange creatures with frightening, alien bodies open a secret doorway in the smart matter tunnel wall, revealing a huge cavern within the mountain. The beings carry huge, mysterious metal cylinders inside before the train gets moving again. When Miki and Aya report what they've seen, Jai decides to use a very-illegal matter-hacker to break inside to find out what's going on.
Once inside, the Girls immediately have fun exploring the huge space within, filled with dusty equipment and the strange metal cylinders they saw the alien-like creatures bring in. But before too long, the shadows start playing tricks on them and they begin to grow uneasy. Miki even thinks she sees something following her and Aya, and runs back to get the other Girls.
Aya discovers with relief that its only Moggle, whom she's rescued and coated in black camo paint so he can better spy on the Sly Girls without their knowledge. She orders her little hovercam to hide, so it does, inadvertently leading the Sly Girls to an airlock chamber. As they wait for Eden to explore it, Aya secretly uses her eyescreen to look through Moggle's point of view and sees that he's found a way outside at the top of the mountain, with a perfect view of an unscheduled mag-lev headed straight for them. Jai, now called Kai, had left the secret door wide open, and Aya knows that the powerful wake of the train could suck everything not tied down, including their boards, into its slipstream.
When Aya tells Kai, Kai doesn't really believe her - how could she know a train is coming? - but the risk is too great to ignore. As they get close to the open door, the Girls can unmistakably feel the train rumbling on its way. Eden frantically tries to close the door, managing to work the matter-hacker's controls just in time. A relieved Kai thinks that's enough fun for one night, but nevertheless allows the Girls to swipe various objects from the disorganized jumble of equipment within the mountain.
Soon after, Aya becomes famous as the Slime Queen because she had been seen with the famous Frizz Mizuno covered in muck. She had just rescued Moggle from the city storm drain, and although Moggle was off chasing toy war-wheels, Kai and Eden spot it flying around in the background and their suspicions that their newest member has been lying through her teeth the whole time are confirmed. Kai decides to let Aya think they're still being fooled, however, and bans her from the group until her face rank drops back down to six figures.
- Eden Maru seems to be Ai's second-in-command, despite being the most famous member of the Sly Girls.
- As Ai scolds the Girls for using her nickname too much, she complains that her face-rank has risen almost above the bottom thousand, meaning her face rank is usually around 999,000.
- After Aya's City Killer story kicks, Ai's face rank rises to 957.
- When Ai sends Aya her first invitation to mag-lev surf with the Sly Girls, the ping is anonymous and decorated with animations of winking, Plain-Jane eyes.