Ryoka Saiga

Ryoka Saiga, also known as the Scissors Lost Smash, true name unknown, is one of the two secondary antagonists of Kamen Rider Build: Be the One film. She is a member of Blood Tribe and one of Evolt's cohorts.

After the unification of Japan, Ryoka Saiga became one of the new governors of the three regions alongside his fellow Blood Tribe members Kengo Ino and Mitsuomi Gohara. The three would then enact their own plan to destroy Earth in the stead of Evolt, who abandoned their cause of destroying it in order to pursue his own goals.

She is portrayed by Rena Matsui.

Past
Ten years ago, the real Ryoka Saiga was one of the four astronauts on the Mars Expedition alongside Soichi Isurugi, Kengo Ino and Mitsuomi Gohara. They discovered the Pandora Box and were possessed by Blood Tribe members after coming into contact with it. The Blood Tribe members came to Earth where they caused the Sky Wall Incident and secretly conspired to spark the Japan Civil War. During the rise of Faust, Ryoka Saiga served as an adviser to acting Touto Prime Minister, Gentoku Himuro. Ryoka was the one who advised Gentoku into starting a war with Hokuto, thus beginning the Japanese Civil War.

Kamen Rider Build: Be the One
The Japanese Civil War later ended when Evolt, in the identity of Seito's Prime Minister Masakuni Mido, used Seito to conquer Touto and Hokuto, unifying Japan under him. He then set up a new government and elected the other three members of the Blood Tribe as the new governors of a unified Japan in their assumed guises as the three former astronauts.

However, Evolt also abandoned the Blood Tribe's plan destroy the Earth to instead have more fun (though really it was to pursue his own secret plan of obtaining the power of warp travel via the Black Pandora Panel). Dissatisfied, the other three members of the Blood Tribe met with Evolt and said they would take the task to their own hands. Amused, Evolt tells them he would not interfere and offered them the Cobra Lost Bottle, Zebra Lost Bottle and Scissors Lost Bottle, though at the same time telling them he still had the upper hand since he had the Pandora Box's power.

After becoming governor, Ryoka and her cohorts began the Build Annihilation Plan, where they used a nation-wide broadcast to brainwash every single human in Japan, including Misora Isurugi and Sawa Takigawa, into hunting down Sento and other Kamen Riders in a national manhunt.

In their final confrontation, the three governors faced off against Build and his allies while surrounded by civilians still under their control. While Build fights Kamen Rider Blood, Ryoka transformed into the Scissors Lost Smash to battle the other Kamen Riders. She was destroyed alongside Mitsuomi Gohara as the Zebra Lost Smash by Kamen Riders Rogue and Grease.

Later, after overseeing the Build Annihilation Plan to its end, Evolt decided to restart his destruction plan of Earth. He recovered the three Lost Bottles and mocked his three colleagues' demise, saying their fates were sealed the moment they decided to betray him.