- Written by Shogo MutoDirected by Satoshi Mogoto
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. However, the Pandora Box was stolen from the Institute and the bottles needed for Build's transformation were taken. Sento and his companions had found themselves in a dire predicament.
Ryuuga: How many bottles were stolen?!
Sento: One, two, three, four... maybe about sixteen?
Ryuuga: That's way too many! And why carry them all in the first place?! It would make your pockets noisy!
Sento: Don't judge me on how I carry around my bottles! I know what I am doing, all right? Now, what's in store for episode 11?
- Comes Great Responsibility: Sento invokes this towards Ryuuga to make him understand the weight of becoming a rider. He can't transform without strong (and probably unselfish) feelings and a loose cannon like him has a high probability of doing more harm than good.
- Curbstomp Battle: Ryuuga as Cross-Z doles out two in his debut. He takes down Sawa's Smash form in literally one hit, then proceeds to rip Rogue to pieces with the Beat Crosser.
- A House Divided: The discord between Night Rogue and Blood Stark is deepening with each time Stark goes against Rogue to further his own plans. He notably tells Gentoku "Faust doesn't belong to you."
- Wham Line: While this episode doesn't have nearly as many plot points as the others to reveal we do get a juicy one. Apparently Pandora's Box require Full Bottles to do something, and just three are still needed. Assuming that all sixteen of Sento's bottles are being used and none else, that means that nineteen is our magic number.
- Villainous Rescue: Once again, Blood Stalk appears for no explicit reason other than to help Sento and Ryuuga escape when KeyDragon continues to be too much for Sento to handle.
- You Have Outlived Your Usefulness: Sawa told her boss that Misora outed her and continuing the infiltration will be complicated from now on. The next time she turns up is as a Smash. She herself says that she has been cast away after being turned back.
- Heel–Face Turn: Which backfires spectacularly, since Sawa now intends to tell our heroes everything they're in the dark about, since they clearly care for her more than her old employers have.
- Full Bottles needed for Pandora's Box Activation: 3
