- Written by Shogo MutoDirected by Shojiro Nakazawa
Sento: The brilliant physicist, Kiryu Sento, fights to protect Touto as Kamen Rider Build. He sets off to prove Banjou Ryuuga's innocence by trying to solve the mystery of Katsuragi Takumi's murder.
Ryuuga: Why are you being so calm about recapping the story!? You might've been the one who killed Katsuragi Takumi!
Sento: Hey, don't drag personal circumstances into the recap.
Ryuuga: Did you kill Katsuragi and frame me for it?!
Sento: Well, they're supposed to find out by watching the episode! That said, what'll happen on Episode 7?!
According to Tatsuya’s testimony, the allegations surrounding Katsuragi Takumi’s murder now turns towards Sento! He revealed that Taro Sato, Sento’s former self, was visiting the victim's room on the day of the murder shortly before Ryuuga found his body. The ex-pro fighter now grills Kiryu about him being the real culprit, but ends up getting nothing of value from him since he's amnesiac. It is just then when Itsurugi makes a sudden proposal. “Maybe you should be investigating Katsuragi Takumi instead.” The search for the truth behind the "Devil's Scientist" begins, and it leads them towards Hokuto - which is something that Faust very much doesn't want them to do...
- Accuser of the Brethren: Even though the evidence so far points to something happening in the hour between Sento and Ryuuga’s respective arrivals to the late Takumi’s address, Ryuuga is convinced that it has to be Sento who killed Takumi, which Sento, as an amnesiac and counting each accusation, dismisses as baseless.
- Cash Gate: The Sky Road, land paths that lead through the Skywall without killing people, that aren’t protected by border guardsmen effectively become this as human traffickers will only lead people through and away the Sky Roads as long as they have enough money.
- Gun Struggle: A variation of this when Ryuuga tries to wrestle the Steam Rifle out of Blood Stalk’s hands, ending with Ryuuga managing to take the Rocket FullBottle out of the rifle.
- It Makes Just As Much Sense In Context: Nobody understands why Ryuuga is wearing a clown costume when he and Sento were going to cross the Skywall into Hokuto. It gets worse when it doesn’t even manage to protect his identity as a couple of kids draw attention to Ryuuga and then pull off his nose.
- Kick the Dog: In tandem with Would Hurt a Child, there was no reason for Blood Stalk to randomly convert Takehiko into the Ice Smash when he was more than capable of fighting off Build, but it happens anyways.
- Outrunning the Fireball: What the Rocket Steam Attack looked like at first, before it redirected itself and attacked Night Rogue, allowing Sento and Ryuuga to escape into Hokuto.
- The Reveal: Four:
- Gentoku Himuro was actually Night Rogue this entire time
- Faust is something he commandeered in secret
- The Rider System is actually a military development that Gentoku intends to use for Touto,
- Lastly, Faust was founded by Takumi Katsuragi.
