The mysteries of the past continue to pile up as Sento investigates the Pandora's Box disaster. In Seito, Ryuga and Sawa continues the search for Nabeshima's family.

Sento confronts Owner on his involvement with Faust. Sawa finds a lead on Sento's elusive past.

Ryuga finds the entrance to Faust's hidden base. Aiming to learn more, Sento learns of the late Katsuragi's research into "Nebula Gas".

Sento and Ryuga need to learn more about Katsuragi and his research. Setting their sights on Hokuto, they first have to get through the Sky Wall...

Now hidden in Hokuto, Sento and Ryuga try to learn more about Takumi Katsuragi from his mother, and find his hidden project data.

A debate about the nature of Katsuragi's research leads to another falling out between Sento and Ryuga. Under pressure from a backer, Faust hatches a plan to steal Pandora's Box.

As the three Prime Ministers of Japan meet, Blood Stark leads an attack on the Touto Institute of Advanced Matter Physics.

With the majority of his Full Bottles now in Night Rogue's possession, Sento reveals his trump card - a way for Ryuga to use the Build Driver.

Sawa reveals a connection between Faust, Nanba Heavy Industries, and the Touto Government. Sento and Ryuga plan to recover Pandora's Box.

A surprise call from Nabeshima lays the foundation for Sento's plan to reclaim Pandora's Box, and a chance to capture the elusive Blood Stark...

Blood Stark's identity is revealed, and Sento races against time to finish a counter-measure against him.

Gentoku reveals the truth behind Sento's missing memories, and the reality may tear his and Ryuga's friendship apart.

Hokuto invades Touto, looking to claim Pandora's Box for themselves. As civilian casualty numbers raise, Gentoku's government instigates Kamen Rider as their military weapon.

Another clash between the Touto and Hokuto Riders ends with Ryuga struggling from the Sclash Driver's effects. The Hokuto Crows are given a way to power up by Blood Stark, but there's a cost...

Soichi gives Sento the means the stop Ryuga's growing rage with the forbidden item - the Devil's Trigger. Gentoku plots a counter-attack against Hokuto's invaders.

In order to counter Ryuga's rampage as Cross-Z Charge, Sento is forced to use the Hazard Trigger. What is the cost of using this forbidden item?

Touto and Hokuto's governments have ordered a winner-takes-all battle to decide who keeps Pandora's Box. It's Build vs Grease to decide the victor of the Rider War!

Seito delivers an ultimatum to Kazumi - fight for them as their Kamen Rider or witness the death of his family. A mysterious new adversary makes his way to Touto to confront Sento and Ryuga.

Kamen Rider Rogue has revealed himself; Misora collapses inside the base.

Kamen Rider Rogue receives the data on Build's Rabbit Rabbit form, forcing Sento to unleash Tank Tank form; Sawa's backstory is revealed while Kazumi rescues civilians; Nanba decides to not play fair, taking control of Seito and declaring war.

Despite their promises, Seito continues their assault against Touto. All this is made worse as Blood Stark completes a panel of Pandora's Box, and the Skywall begins to shift...

Blood Stark wonders how the Queen of Mars is still alive. Mysteries begin to arise as she singles Ryuuga out to become hope.

Sawa and Misora discuss what the story behind Ryuuga really is; Team Build raid Pandora's Tower in an attempt to reclaim Pandora's Box, but Blood Stark stays one step ahead, goading Ryuuga into action.