- Written by Riku SanjoDirected by Satoshi Morota
Kiriko reports to Shinnosuke of another case, where they are tasked to scan Heavy Acceleration particles at the Metropolitan Police Forensic Science Lab. Forensic Technician Mariko Minowa (a fan of Shinnosuke/Kamen Rider Drive) reports that while she was eating at the lab, a Heavy Acceleration wave was released and several files had been stolen though she had no idea of whom it belonged to. Suddenly, the Shift Cars have track the culprit as they are fighting it, whom turns out to be the Fusion Evolution State Roidmude Thief Roidmude. Thief tries to run but forces to fight Drive and during the conflict, a file that was stolen ejected from his body. Panicked, Thief endangers several civilians and Drive assumes Type Tridoron People Saver, capturing Thief in Justice Cage, saving an injured victim with Cure Quicker and rescued a nearly fallen one with Ladder Expander. Brain appears and saves Thief from his imprisonment. Brain lashes Thief for being clumsy, having depressed after the theft of his tablet (Tenjuro Banno) and his favourite senior's demise. Brain assures that he will achieve Super Evolution and become a member of the Promised Number.
As revealed by Genpachiro, Shizuo Shigeta (59 years old), the head of forensics lab physical department had been reported missing a few weeks ago. Kiriko suspects him as a host for the Fusion Evolution State but Mariko denies it, knowing him as a honest person. She suddenly knows what was stolen which is the evidence Shizuo was looking for. Witnessing one of the files that dropped by Thief Roidmude, Shinnosuke realizes that the cases are the ones that related to his father's death from 12 years ago.
At the Unit'd office, Nira decided that they need to keep this a secret for a while. Those who had recovered from Freeze's memory manipulation start to regain their true memories. Nira is at wit's end as he was forced to hold the responsibility for Makage's death. Capt. Shizuo coincidentally was investigating the robbery from 12 years ago, thus being targeted by Thief. Shinnosuke remembers the gun that killed his father may had a piece of evidence, and Nira gives him a list of facilities that used by Makage and theorizes that one of them may be secretly affiliated to him.
As Shinnosuke and Kiriko storms one of the facility listed, Heart appears and challenges Shinnosuke. He demonstrates his Super Heavy Acceleration ability, with Shift Deadheat and Formula come to rescue Kiriko and Drive. To make up for his failures, Brain offers himself to attack Kiriko, but finds himself facing Chaser. Chaser calls Drive for a retreat as Drive cancels Heart's Super Heaviness and escapes. Go at the same time tries to find a place to house Dr. Banno's A.I., and for the first time acknowledge him as a father. Shinnosuke wonders how Heart is capable of finding him in the facility, thus sensing something else.
At the Unit's office, Jun presents Shinnosuke, Kiriko and Nira a new batch of antidotes manufactured by Rinna. In somewhere else, Thief orders the captured Capt. Shizuo to solve the case, giving him the stolen evidences. Shizuo realises that the bullet is from a different gun than the one that shot Eisuke. Brain and Thief forces him to remember back the gun that he hid 12 years ago while he was under Makage's spell. Jun appears and reveals that the gun has his fingerprints, making Thief's host as the murderer of Eisuke. With Makage died, he feared that the erased memories will appear and thus fused with the Roidmude to destroy the evidence. Drive appears and separates Thief, revealing Roidmude 106 and worst, Mitsuhide Nira. He was the only one knew which facility Shinnosuke and Kiriko were after and they put up an act to track him with the antidote bottle that placed with a tracker.
Nira reveals that he and Eisuke are partners and he grew jealous of Eisuke's escalating success. He tried various ways to get famous but Eisuke outsmarted him and advice not to take shortcut in solving cases. What happened in the robbery from 12 years ago was not a coincidence. Makage/001 lured Eisuke to the bank with an anonymous tip. He and Nira entered the bank in disguise of ordinary customers and when the robbery happened, Eisuke covered a little girl when she cried. Itsuro Negishi was just pointing his gun to Eisuke and when his acquaintance, Maruya stepped back, Nira secretly knocked him. Negishi decided to dropped his gun but while doing so, Nira, whom was targeted him switched to Eisuke and instead killed him out of jealousy. It was then 001 appeared and erased the memories of everyone from the robbery but ordered Nira to obey him for the price. He hid the gun as long as Nira had his loyalty for 001. Makage soon orders Shizuo to hide the real gun and the shooter's identity while erased the latter's memory from it.
Nira's jealousy spiked and Brain orders 106 to re-merge with him to become Thief Roidmude. Drive as Type Tridoron fights Thief and managed to separate him from Nira but once did so, Brain brings Nira away and turns 106 into a Giant Bat Roidmude. Drive rides Booster Tridoron and finishes 106 with Rider Break.
Shinnosuke tries to search the gun but realises it has been taken away. The forensics decided to help him from inside by finding other evidences as alternatives. At the rooftop, Brain absorbs Nira's jealousy and finally gains his Super Evolution.
- Breather Episode: While still having the twist of the true murderer of Shinnosuke's father, this episode is nowhere near as dark as the previous few.
- Dirty Coward: The Thief Roidmude (a Hybrid Evolution of 106 and Nira), acts and fights like this. He tries desperately to escape Drive during their initial confrontation, going so far as to collapse a walkway to force Drive to abandon pursuit in order to help the casualties.
- Don't You Dare Pity Me!: Tragically, Eisuke's well-meaning advice is taken by Nira as Eisuke looking down on him.
- Green-Eyed Monster: Nira was insanely jealous of Eisuke, Shinnosuke's father. Despite entering the force at the same time, Eisuke was just so much better Nira hated his guts.This is what drives Nira into killing Eisuke.
- Humans Are the Real Monsters: Nira spits this out to Shinnosuke, claiming that everyone has a dark side to them. This is apparently the dark truth Freeze mocked Shinnosuke with, it wasn't a Roidmude plot that killed his father, it was nothing more than simply human pettiness and jealousy.
- Not So Different: Brain initially decides to abandon Nira to Shinnosuke and the SCU, but after hearing his Motive Rant realises that they're the same sort of person and goes to aid him.
- Pragmatic Villainy:
- The Thief Roidmude is something like this as well. His primary objective is to recover some evidence from a police lockup, and he tries to flee as soon as he realises Drive is there. He also deliberately risks the lives of nearby people, knowing Drive would abandon the pursuit rather than let innocent people get killed.
- In an attempt to regain his tablet (stolen by Gou), Brain immediately goes after Kiriko. He also waits until Drive is busy fighting Heart, but is eventually driven back by Chase.
- Sore Loser: Kiriko suggests that Freeze's claim that there was another secret behind Shinnosuke's father's death are simply a few last words cast out by a sore loser.
- The Powerof Hate: Brain is able to achieve his Ultimate Evolution by meeting someone whose Envy matches his own.
- The Quisling: Previous episodes suggested Nira was 001's patsy, working for him because 001's human form Makage was Defense Minister. As it turns out, Nira was well aware that Makage wasn't human.
- Villain Forgot to Level Grind: Once again subverted by Heart, as Medic has upgraded him further using ideas she got from when she'd modified Chase many episodes ago.
- Villainous Legacy: Despite his death, 001's shadow still looms over the story, as he made it possible for Eisuke's murderer to evade justice, his Hybrid Evolutions are still a threat, and he has now shown the other Executors the way to achieve their Ultimate Evolutions.
- The Roidmude Count: 55The Answer: Captain Mitsuhide Nira, driven mad with jealousy