- "F" stands for "Fuyumi (Asoh)" and "Fang (Gaia Memory in its in-series debut)"
- Part one's title is "Burglary Rider".
- Part two's title is "Reclaim your partner".
Philip trains himself and sees a dinosaur-shaped Memory. Meanwhile the Detective Agency gets a customer named Fuyumi Aso who asks them to find a Kamen Rider. It turns out that said "Kamen Rider" is but an impostor Dopant who has gone on a crime spree. After the Dopant robs an armored truck Shotaro arrives as Double to intercept him as the Dopant flees. Fuyumi Aso then reveals that she was one half of the Twin Rose burglar team, of whom Kenji Kurata, the Arms Dopant, was the other half.
Shotaro confronts Kurata, ordering him to discard the Arms Memory. Kurata refuses and transforms into the Arms Dopant, and fights Double until Kurata springs a trap. Akiko and Fuyumi are captured by Masquerade Dopants, and Arms threatens to kill Akiko if Double does not cancel his transformation. Though Shotaro intends to outwit Arms with Philip's help, Arms disables the right side of the Double Driver. Upon Arms revealing his target as Philip, Shotaro tells him to flee. With Masquerade Dopants on his tail, Philip runs into Saeko, the mastermind of the trap, whereupon she calls Philip Raito, the chosen child.
Philip then attempts to escape, encountering the Fang Memory once more. Resisting its offer of power once more, Philip rides the RevolGarry, leaving Shotaro and Akiko behind. Kurata makes a call to him, demanding Philip's surrender in exchange for letting Shotaro live. While contemplating a way to rescue Shotaro and Akiko, Philip is visited by Watcherman, Santa-chan, and Makura, all looking for Shotaro. Philip also runs into Fuyumi, whose determination to get her partner back eggs him on.
Meanwhile, Shotaro and Akiko are caught in Kurata's sadistic trap, with Akiko's bleeding hands holding a rope preventing Shotaro from falling on spikes. Shotaro notes that the only way to escape is through the use of the Fang Memory, which weighed heavily on Philip's mind and body. The two are rescued by Philip and the Fang Memory, and the younger man transforms into Double FangJoker.
FangJoker fights in a berserk rage, overwhelming the Masquerade Dopants sent its way. Only the Arms Dopant stands in its way, and Double attacks Arms, almost slashing Akiko, just as Shotaro finds his partner within the burning Gaia Library. With Shotaro and Philip united, FangJoker is under control, avoiding Akiko. Double confronts Arms, defeating him with the newly named Fang Streiser Maximum Drive. Shotaro takes point and chases after Saeko as LunaTrigger.
Just as Double confronts Saeko as the Taboo Dopant, Kirihiko as Nazca saves her with his newfound speed. In the process Shotaro saves the reputation of Kamen Rider in front of Jinno by rescuing a girl.
As the case is closed, Shotaro wonders of things to come, as the Fang Memory encounters a blue beetle-like device...
Tropes within the arc include: