Kazumi and Gentoku infiltrate Faust's headquarters in Hokuto, but Utsumi appears to face them. Meanwhile, Sento confronts his father, who reveals the true reason why he joined forces with Evolto.
With Sento confused with the fact that his father might be in league with Evolto, another person transformed into Kamen Rider Build appears before him.
Sento discover that his father is alive, and by searching the files he got from his mother, he learns why the Rabbit and Tank Full Bottles have a special meaning to him.
Having finally opened the Pandora Box, Evolto almost destroyed the world, should Vernage had not interfered. However, Sento has run out of options, and decides to risk it all in a move to defeat him.
Having attained the power to transform into Kamen Rider Evol, Evolto infects Sento with a poison, threatening his life should he not relinquish the Fullbottles in his possession.
As the Riders invade the Pandora Tower to retrieve the Pandora Box, a new power bursts from Ryuga, just as questions about his true identity are raised.
Vernage, the Queen of Mars possesses the body of Misora to assist the Riders in retrieving the Pandora Box, revealing an important secret about Ryuga in the occasion.
The war between the nations has ended, but Soichi and Namba finally reveal their true intentions as a new conflict begins when they open the Pandora Box.
Seito challenges Touto for another proxy battle to end the war once and for all. Sento and his friends make preparations to confront Gentoku and his subordinates, unaware that one among them is a traitor.
Gentoku reappears as Kamen Rider Rogue, determined to get revenge on Touto. To stop him, the other Kamen Riders decide to join forces, when Sento perceives something strange happening with Misora.
Taking advantage of the conflict, Seito invades and conquers Hokuto. Now bent on seizing all of Japan, the Seito forces invade Touto, led by the mysterious Kamen Rider Rogue.
Sento and Kazumi have a duel to settle the war, but when the enemy proves himself too strong for him, Sento has no option but to use the Hazard Trigger again.
Despite knowing the risks, Sento uses the Hazard Trigger to empower himself against Kazumi's three subordinates. After losing his consciousness and killing one of them, Sento is struck with guilt and refuses to keep fighting, until Soichi gives him an alternative.
Sento and guys were driven into a situation where they had to hide Pandora Box in a old warehouse. They make a decision to uncover a government conspiracy.
After learning from Sawa about the connection between Faust and Nanba Heavy Industries, Sento and Ryuga confront them to retrieve the Pandora Box and their stolen Full Bottles.
Sento and Ryuga discover that Katsuragi was involved in creating a Build Driver of his own, and his possible involvement with Sento widens the distrust between them.
Sento discovers that Katsuragi was the founder of Faust, and approaches his mother to learn more about Katsuragi's intentions, and obtain more clues regarding his lost memories.
After getting another of his memories back, Sento investigates the connection between Faust's experiments and the Pandora Box; Ryuga tracks down Nabeshima's family and stands up to protect them from the enemy.
Because of helping Ryuga, the government chased Build as a wanted criminal. Sento guesses that he can obtain clues to the mysterious organization by finding true culprit who killed Katsuragi.
Unidentified creatures called Smash have appeared at Touto, Sento Kiryu turns into Kamen Rider Build to fight against them. One day, he saves a guy named Ryuga Banjo who escaped from a prison.