Stalk: A war's erupted between Touto and Hokuto over the immense energy within Pandora's Box!
Kamen Rider Build, Kiryu Sento, loses his will to fight after destorying one of Hokuto's Smashes,
but to protect Touto, he will fight Hokuto's Kamen Rider Grease in a proxy battle!
Ryuuga: What are you doing the intro for?
Stalk: My voice is great, right? I always get the job done in that regard!
Ryuuga: Don't call it a job!
Stalk: Now, what'll happen on Episode 22?Kamen Rider Build has chosen to represent Touto in the battle against Hokuto's strongest Rider, Grease. The victor will claim the Pandora Box and the war's victory. Getting prepared for this kind of fight is not easy. Sento has decided to rise up to end the suffering and protect the city of Touto. Sento wants to avoid using the dangerous power of the Hazard Trigger as much as possible, but when Grease proves to be too strong, he reaches for it.
- Big Damn Heroes: Cross-Z Charge comes to get Build to stop rampaging after his victory and manages to land a powerful punch that knocks him out of his transformation.
- Chronic Backstabbing Disorder: Per the course with Blood Stalk, his goal was to backstab Hokuto and align with Seito, who he also gave the Sclash Driver data. Yoshiko ends up having to surrender since he "suggested" for her to send all of Hokuto's troops with none to defend her.
- Curb-Stomp Battle: Both Build and Grease go back and forth with each other on this until Build uses the Hazard Trigger. Then, it's Build who's in control of the fight.
- Early-Bird Cameo: At the end of the episode, a new Kamen Rider named Rogue makes his appearance.
- Marathon Boss: The fight between Build and Grease seems to go from early evening until around night time until one of them is the winner.
- Neutral No Longer: Seito, by then end, has decided to be on the front lines now, with their first act being to invade Hokuto.
- Not So Different: When Ryuga points out how Sento is scared of the Hazard Trigger's danger, Sento shoots back that Ryuga himself is scared of the Scalsh Driver's danger. It takes Ryuga facing off against Hazard Build that he finally controls the Driver's power.
- Self-Destruct Mechanism: Sento developed one for the Hazard Trigger. Should he go berserk, Misora could just use a special switch to destroy the Hazard Trigger, at the cost of Sento's life. While Misora is not happy about that, she fortunately does not have to use it as Ryuga managed to knock Build out of transformation.
- Wham Episode: With Build winning, Touto wins the war against Hokuto. But, Blood Stalk uses this opportunity to have Seito invade Hokuto and make Yoshiko their prisoner.
- Xanatos Gambit: Earlier, Blood Stalk convinced Yoshiko to move all their forces to the lines of Touto if they win or lose. Not that he cares of course as without no military close by, it gave Seito the opportunity to storm Hokuto's government.