Kamen Rider Build

Main Two Kamen Riders: Build and Cross-Z

 Kamen Rider Build is a Japanese tokusatsu drama in the Kamen Rider series of Toei Company. It is the nineteenth series in the Heisei period, and the twenty- eighth overall.

Ten years ago, a Martian expedition crew brought a mysterious artifact, the "Pandora Box," to Earth. The artifact was activated during a national conference that caused a massive catastrophe in the form of a Skywall that divided Japan into three regions: Seito in the west, Hokuto in the north and Touto in the east, with each region holding the fragments of the Pandora Box.

In present time, a genius physicist named Sento Kiryū is hired by the government- funded Touto Institute of Advanced Matter Physics to uncover the secrets of the Pandora Box. But Sento, having no memory of his past other than being held captive by the mysterious Night Rogue of the Faust organization, secretly shines on the side as Kamen Rider Build to fight the Smash monsters created by the victims of Faust 's experiments.

Helped by cafe owner Soichi Isurugi and his daughter Misora, who can purify Smash elements, Sento also became friends with a framed fugitive named Ryūga Banjō, who escaped while experimenting with Faust and eventually became a Kamen Rider Cross-Z.

The two Kamen Riders eventually learn that Night Rogue is none other than Gentoku Himuro, son of Taizan Himuro, Prime Minister of Touto, and that his former ally Blood Stalk is Soichi, who caused the Skywall disaster and works with industry mogul Juzaburō Namba to manipulate the nations to declare a civil war, which in reality is a ploy to reassemble the Pandora Box.

Kamen Rider Build

The revelation worsens when Sento learns that he was actually Faust's founding member, Takumi Katsuragi, Soichi, who wiped his memories while changing his face to that of the deceased musician Taro Sato. Hokuto sends Kazumi Sawatari, a soldier who can transform into Kamen Rider Grease, together with his own army to steal Pandora Box and Fullbottles from Touto.

Although Sento managed to defeat Kazumi after their nations agreed to settle things in a decisive duel, Seito took this moment to conquer a defenseless Hokuto. Seito then turns his attention to invade Touto, assisted by an exiled Gentoku who is able to transform into Kamen Rider Rogue, with Kazumi joining Sento's group to liberate Hokuto. But it was during this battle that Sōichi was revealed to be an unwilling host to Evolto, a mysterious extraterrestrial entity responsible for wiping all life on Mars and the true master of all catastrophes.

After unleashing the true power of a nearly complete Pandora Box, Evolto eventually managed to gain back the Evol Driver and Evol-Trigger to transform into the nigh-omnipotent Kamen Rider Evol. He also revealed that Ryuga is actually a part of himself, transferring himself into Ryuga’s body in order to gain even more strength.

Evolto kills Namba and his cohorts after they no longer need them. A repentant Gentoku joins Sento to stop the alien, as the latter regains his memory as Takumi and acquires the means to fight a fully corporeal Evolto on equal ground.

While Evolto was helped by Namba's former assistant Nariaki Utsumi after becoming Kamen Rider Mad Rogue and Takumi's father Shinobu Katsuragi, the alien did not know that the two were acting against him, as Shinobu gave Takumi the means for him and Ryūga to destroy Evolto once and for all.

With Evolto managing to fully restore the Pandora Box, the final battle for humanity ends with the death of the alien when Sento caused the Pandora Box to assimilate its reality into the "Prime" Kamen Rider world, creating a new world where the Skywall incident and the resulting tragedies never happened. While sad that none of their friends remembered them and their times together, Sento and Ryūga decided to start making a new life for themselves in this new reality.