Kengo Ino

"Attack every planet in the universe and destroy their every bit... This is the duty of we Blood Tribe!"

- Kengo Ino

"Kengo Ino", also known as Kamen Rider Blood, is the main antagonist of Kamen Rider Build: Be the One film. He is a member of Blood Tribe impersonating as the new Governor of Touto. After the unification of Japan, "Kengo" took part as one of the new governors alongside Ryoka Saiga and Mitsuomi Gohara in order to destroy Earth in the stead of Evolt, whom they believed to be a failure of their race.

He is portrayed by Masanobu Katsumura.

History
Ten years ago, the real Kengo Ino was one of the four astronaunts on the Mars Expedition alongside Soichi Isurugi, Ryoka Saiga and Mitsuomi Gohara. They were possessed by Blood Tribe members after the discovery of Pandora Box. The Blood Tribe members conspired to each other and started the Sky Wall Incident, along with Japan Civil War.

Nevertheless, Evolt left the trio and started his own plan in destroying the Earth. During the rise of Faust, "Kengo" served as the advisor of Seito Prime Minister, Masakuni Mido.

Kamen Rider Build: Be the One
Ten years later, after the end of Japan Civil War, Evolt conquered Touto after taking over Seito. Soon, the other three members were promoted to be new governors of a unified Japan, as they impersonated as the three former astronaunts.

However, due to Evolt's renouncement on destroying the Earth, the other three members of Blood Tribe were dissatisfied. They met with Evolt and said they would take the task to their own hands. Evolt agreed and offered them Cobra Lost Bottle, Zebra Lost Bottle and Scissors Lost Bottle, but he claimed he still had the upper hand since he had the Pandora Box's power.

After becoming the new governor, Kengo soon started a new project known as the Build Annialation Plan, starting 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. He also brainwashed Ryuga Banjo and turned him against Sento, before gaining Ryuga's Build Driver and Great Cross-Z Dragon. Combining them with Sento's Hazard Trigger and Cobra Lost Bottle, Kengo managed to transform into Kamen Rider Blood while claiming he had obtained the power for destruction.

Later, Kengo called Sento to give in the Pandora Box in exchange of Ryuga. In their final confrontation, Ryuga, Kengo, Mitsuomi and Ryoka are outside, surrounded by civilians still under their control. Sento arrives on his bike with the colored panels of the Pandora Box. Fusing with Ryuga, Kengo transformed Kamen Rider Blood and Sento goes straight to Genius Form, with the two remaining governors transformed into Zebra Lost Smash and Scissors Lost Smash respectively. Kengo revealed that his encounter with Ryuga was something they orchestrated and managed to outmatch Sento. Sento recalled the memory where his father told him that Ryuga holds the key to all the events to come. Sento asked why he became a scientist and his father replies for "Love & Peace".

In the climax of their battle, manages to pull Ryuga out of Blood. Blood takes the Pandora box down into the ground, heading for the center of the Earth to destroy the planet. With the help of Vernage inside her, Misora regained her senses and healed everyone from the Blood Tribe's control. Ryuga and Sento then fused themselves into Cross-ZBuild Form. They headed down to fight Blood and while they initially struggle to control their new form. In the end, they forced Blood back to the surface and perform the Love & Peace Rider Kick, destroying Blood just in time when Gentoku and Sawatari destroyed the remaining Blood Tribe governors, ending their terror.

Later, Evolt collected the three Lost Bottles and mocked his three colleagues' demise, saying their fates were sealed the moment they decided to betray him.

Trivia

 * It is assumed that the real Kengo Ino, at least his New World counterpart formed after Evolt's demise, is still alive somewhere in spite of his Blood Tribe counterpart's demise.
 * Before the reveal of Blood's name, many fans assumed from the promotional picture of Be the One that Kamen Rider Blood was a darker form of Cross-Z taken by Ryuga after being brainwashed by the Blood Tribe. However, it was debunked after the name of Kamen Rider Blood was revealed.