- Written By:Shogo MutoDirected By: Kazuya Kamihoriuchi
Sento: A civil war has erupted over the incredible energy hidden within Pandora’s Box. Kamen Rider Build aka Kiryu Sento attempts to fight off an invasion by Seito, currently taken over by Nanba Heavy Industries. He heads to retrieve Pandora's Box and end the war, but then...
Vernage?: My name is...
Sento: You're the Queen of Mars?!
Misora: Everyone's idol, Miitan!
Sento: Quit trying to capitalize on the Plot Twist about the queen to get laughs! Now, what'll happen on Episode 31?!
Episode Tropes:
- Call-Back: Remember all those times Ryuga tried to talk about his life story, starting with his birth? Yeah, turns out that was relevant all along.
- Even Evil Has Standards: Rogue seems to disagree with how Nanba plans on using Pandora's Box (in contrast to his own plans of making Kamen Rider soldiers and using the box as a deterrent to unify Japan, Nanba wants to rule the world). He actually fights Sento and tells him that Nanba is impersonating the deceased Midou.
- Express Delivery: According to Sawa, Ryuga was born in two months of his mother's pregnancy.
- Heroic BSoD: Ryuga suffers one when it turns out Kasumi's transformation and death were all part of Blood Stalk's plan to make his Hazard Level grow.
- Perpetual-Motion Monster: This episode introduces the new Clone Smash, which do not require a human host and does not respond to damage, all while being as seemingly powerful as a Hard Guardian. Stalk himself says that the only way to get rid of them would be to destroy them because they'll keep fighting until they're dead.
- Self-Destruct Mechanism: Gentoku reveals that he has a chip inside him that will kill him if he goes against Nanba's plans, hence why he tells Sento everything he knows in secrecy during their fight.
- Wham Shot: Two near the end:
- Ryuga was able to use the Pandora Box's power in the same way as Blood Stalk did.
- It's revealed that the person who researched Ryuga as a child was Shinobu Katsuragi. Takumi (Sento's) father!
