- T stands for Triceratops, a reference to the Monster of the Week, and transfer.
- Part one's title is "A Melody Not Intended For Women".
- Part two's title is "The Man Who Cannot Die".
Ryu Terui, also known as Kamen Rider Accel, and Makura prepare to arrest Himuro, a police inspector who leaked information to Gaia Memory dealers. As they make the arrest, however, Masquerade Dopants ambush them, with Terui transforming into Accel to defeat them. Terui finds Himuro dead, killed by the Triceratops Dopant who eludes the police Rider. He is then saved from a Masquerade Dopant by Aya Kujo, a Futo officer who worked for the LAPD.
Makura then approaches Shotaro to aid in Himuro's case in order to impress Aya, and given the rivalry between Shotaro and Ryu, he accepts. With Watcherman and Akiko accompanying them, Shotaro learns that Himuro's partner was another corrupt cop named Ken Akutsu. Shotaro and company find Akutsu just as Ryu and Aya find him, until Makura blows the operation, allowing Akutsu to flee. Ryu chases after Akutsu until the Triceratops Dopant appears. Shotaro assumes Double form, transforming into HeatMetal and hitting the Dopant on the leg. Akutsu, while still at large, drops a clue that Ryu finds: a keychain with the name Catherine on it. Everyone returns to the Agency, and as Aya Kujo briefs everyone on her former partner Masaki Mizoguchi, who disappeared and was discredited, Philip notices something amiss with her leg. Ryu also learns of Kujo's love for Mizoguchi.
Meanwhile, as Saeko scolds her sister Wakana, she is contacted by Akutsu, requesting her help. With Philip's help, the group learn that Catherine is the name of Akutsu's boat, whereupon he is cornered. He confesses that with Himuro they sent criminals as Gaia Memory test subjects, with Mizoguchi being killed after he learned too much. The Smilodon Dopant arrives and distracts the Riders, allowing Akutsu to escape on his boat. However, the Catherine is destroyed by the Triceratops Dopant, who is revealed by Philip and Ryu to be none other than Aya Kujo.
It is revealed that Philip guessed it was Aya because of him noticing her leg, as Ryu tells her to give up the Triceratops Memory. Accel then attempts to get the Memory by force but is interrupted by Double, allowing Aya to escape. Shotaro makes one more attempt to get her to come round, by working out the actual location where Mizoguchi died, and conveniently finding her there. With the last of her targets down, she agrees to turn herself in...
...but not before paying a visit to the last Dopant syndicate location Mizoguchi dug up, taking her Roaring Rampage of Revenge to the source. Only she stops just short of taking down Saeko, and instead makes a deal with her, using her Dopant Memory to get rid of everyone remaining that knows what she's done ie: both Kamen Riders.
Turns out Phillip was right to act on his Straw Vulcan nature, heading to the police station while Shotaro was slacking off at the local karaoke place with Queen and Elizabeth. Aya not only lured Terui Ryu off and into a trap, but strolled into the police station to target one of the policemen (Mikio Jinno) to prove her loyalty, except Phillip's presence allows him to enable FangJoker and hold her off. Only when Ryu is revealed to have survived the trap is her true goal made known - the real target is all of Fuuto, the society that depended on Mizoguchi to protect them, and cast him out like a leper based on some rumors. She goes into One-Winged Angel mode and directs her wrath at Fuuto Tower itself, but this time Ryu as Accel has a new weapon, the Gunner-A treaded combat drone, and uses it to bring this case to an end.
- The Ace: Aya Kujo.
- Call-Back: It's the second time a girl with a vengeance gets a dinosaur Dopant form that can go One-Winged Angel.
- Dead Person Impersonation: Played with. The Triceratops Dopant claims to be the dead Mizoguchi, but is actually Aya exacting his vengeance.
- Disposable Vagrant: Akutsu has been supplying Museum with these on the side.
- Foreshadowing: The Triceratops Dopant is designed with a skirt-like section much like the trenchcoat Aya Kujo first appears in.
- Gratuitous English: Aya engages in this during every casual conversation. Its even in her first sentence.Nice to meet you.
- Not So Different: Acting out a personal agenda against the Dopant Memory syndicate while being on the police force - Aya is basically a much-needed reminder of how Ryu might end up.
- Roaring Rampage of Revenge: Aya's entire plan revolves around avenging Mizoguchi's murder... and then she decides to attack everyone who hurt him. Like Futo in general, for example.
- Shout-Out: Gunner-A may have been inspired by WALLE.