Akaba is a member of the Hokuto Three Crows and a supporting antagonist in Kamen Rider Build.



Masaru Ooyama was originally a worker at Kazumi Sawatari's farm along with Syuuya Aikawa and Syoukichi Mihara. When the Skywall Disaster made Kazumi's land infertile, Kazumi used his savings to continue providing for the three and their families. Eventually, after the Hokuto government made a pact with Faust, Kazumi volunteered himself for the Faust organization's experiments so he could continue to support his workers, becoming Kamen Rider Grease and a soldier of the Hokuto government.

Out of loyalty, Masaru, Syuuya and Syoukichi joined the Hokuto military as well and volunteered themselves to be converted into Hard Smash to aid Sawatari as the Hokuto Three Crows. Becoming the Castle Hard Smash, Masaru was code-named "Akaba".

Hokuto-Touto War

After Prime Minister Yoshiko Tajimi declared war on Touto, Akaba and the other Crows were sent in to spearhead the invasion alongside Kazumi/Kamen Rider Grease.

However, after Hokuto sent in all their troops to invade Touto, Seito took the opportunity to invade and occupy Hokuto, easily conquering the country. After Kiba was killed by Seito's Remocon and Engine Bro's, Akaba and Kazumi took refuge with the nascita crew.

Akaba later participated in a scheme to lure out a spy in the Touto government, guarding the Pandora Box while Sento, Ryuga and Kazumi guarded other fake locations. However, Gentoku Himuro managed to find the real location and confronted Akaba to take the Pandora Box from him. Transforming into the Castle Hazard Smash, Akaba fought against Gentoku/Kamen Rider Rogue but was unable to overcome the Rider's fierce fighting style and was defeated. As the fight ended, Kazumi, Sento and Ryuga arrived only to find Akaba dying. As he disintegrated, Akaba thanked Kazumi for all he had done for him before fading into red smoke.

Return as a clone

A clone of Akaba along with clones of the other Hokuto Three Crows were later created by Evolt from his DNA and sent after the four Kamen Riders as they stormed the Pandora Tower. Grease opted to stay behind to fight them, telling his fellow Riders to go on ahead without him. After transforming into Grease Blizzard, Kazumi managed to defeat and destroy all three clones though he died soon after as a side affect of transforming with Blizzard Knuckle.

New World

In the new world created by merging the World of Build into the main Kamen Rider world, Akaba as well as Aoba and Kiba was still a worker at Kazumi's farm. He was seen eating at the nascita cafe with Kazumi and his coworkers and had to catch his boss when he fainted after falling in love with Misora at first sight.



           BUILD LOGO Villains

Night Rogue | Blood Stalk | Takumi Katsuragi | Nariaki Utsumi | Shingo Kuwata | Eita Kawai | Masahiro Nabeshima | Norio Matsui | Yoshikazu Takahashi | Shinobu Katsuragi | Faust Guardians

Yoshiko Tajimi | Blood Stalk | Kazumi Sawatari | Hokuto Three Crows | Akaba | Aoba | Kiba | Massugu Ubukata | Hokuto Guardians

Masakuni Mido | Kamen Rider Rogue | Fu Washio | Rai Washio | Seito Guardians | Hard Guardians

Namba Heavy Industries Ltd.
Juzaburo Namba | Nariaki Utsumi | Fu Washio | Rai Washio | Sawa Takigawa | Kaisei Mogami | Guardians | Hard Guardians

Blood Tribe
Killbus | Evolt | Kengo Ino | Ryoka Saiga | Mitsuomi Gohara

Needle Smash | Strong Smash | Burn Smash | Flying Smash | Press Smash | Ice Smash | Stretch Smash | Fang Smash

Simon Marcus | Keiji Uraga | Phantom Crushers | Guardians | Hard Guardians

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