This article is about a/an villain in Kamen Rider Build.
For the previous "Left Kaiser", see Kaisei Mogami.

―Transformation phrase[src]

"You think you can beat us alone? That make me upset."
―Fu's response to the Owl Hazard Smash challenging him and his brother.[src]

"We're the ultimate weapon of Namba Heavy Industries Ltd., how could we become a scrap so easily?"
―Fu reveal the Kaisers' origin to Ryuga.[src]

"Fighting for someone's sake...wasn't bad after all... I should tell this... to my brother..."
―Fu's last words to Ryuga[src]

Fu Washio (鷲尾 風 Washio Fū) was the older brother of Rai Washio, one of Namba's children hailing from Seito. He is able to transform into the turquoise Kaiser, Remocon Bro's (リモコンブロス Rimokon Burosu).

Character History

Little is known about Fu's past, but he and his brother were raised by Juzaburo Namba institute as his 'Children'. There, Fu and Rai were indoctrinated and trained as soldiers.

Fu, along with Rai was first shown at Hokuto after Kiba defeats Seito Guardians as Owl Hazard Smash. They quickly defeat the latter as Engine and Remocon Bro's easily and taunt Grease to become Seito weapon, if he wants Kiba to live.

After they torture Kiba, Kazumi and Akaba arrive and Kazumi rejects Rai offer and fights him as Grease. Grease, along with Akaba and Kiba escapes, but later shot by Fu using Nebulasteam Rifle. Fu's about to kill Grease, if Kiba didn't take the bullet for him. Akaba later helps his boss escape once more, to Sky Road where Sento and Banjo await.

As Washio brother finally caught up to them, Sento and Ryuga fight them as Build Rabbit Tank Hazard (later Rabbit Tank Sparkling) and Cross-Z Charge respectively, until Rogue make his appearance. The Phantom of the West

Joining Seito's forces in an attack on the Touto government office, the Washio brothers covered Rogue as he went in to claim the Pandora Box, engaging Kamen Riders, Cross-Z Charge, Grease and Build before the latter caught up with Rogue. Eventually, the Kaisers succeeded in defeating the Sclashjelly Kamen Riders. A Man Called Rogue

Alongside Rogue, the Washio brothers represented Seito in a three-stage Proxy Battle with Touto. With Rai having been defeated by Grease in the first round, Fu used his Gear Engine along with his own Gear Remocon to transform into the Hell Bro's as he faced Cross-Z Charge in the second round. The Treacherous Deathmatch Though surprised to find his greater power matched by Cross-Z Charge as his opponent grew continually stronger, Fu was able to goad Ryuga into letting his guard down by claiming that his brother had been taken to custody and scheduled to be terminated should he fail. Fu used Ryuga's hesitation to knock him out of the battle, after which Rai appeared unharmed to gloat with his brother. The Counterattack Hero


After Evolto declares that he will rule the world, Utsumi decides to strengthen the Washio Brothers by injecting them with Nebula Gases. However, even with the conditioning and temporary alliance with Touto Kamen Riders, Evol Black Hole is still too much for them to handle.

After Evol kills Rai with a Miniature Black Hole, a grief-stricken and enraged Fu transformed into Hell Bro's and fights Evol head on. However, Evol manages to defeat him and Cross-Z Magma, whose transformations are cancelled as result. As Evol is about to kill Banjo using the Black Hole Finish, Fu, who had a change of heart after seeing Banjo indirectly fighting for them decides to take the bullet instead. Fu later disintegrates in Banjo's arms, feeling satisfied after he knew that fighting for other people's sake is not bad at all. Mad World


Compared to his brother, Fu is more calm and collected. He rarely speaks, unless when needed. He also prone to make lies, as shown when he told Banjo that if he lose, Rai will be killed. After he defeats Banjo, he shows no remorse and calls him scrap for being too gullible. Both Fu and Rai are cruel and ruthless, and like to torture their defeated opponents.


Nebula Hell Bro's
Nebula Hell Bros

Nebula Hell Bro's

Pre-Hell Bro's

Nebula Hell Bro's is seen during the transformation of Hell Bro's.

Nebula Hell Bro's (ネビュラヘルブロス Nebyura Heru Burosu) is the basic body of the Kaiser with no Gears attached. Though typically bypassed altogether in the transformation to Remocon Bro's, it is briefly seen during the transformation to the combined Hell Bro's. The Counterattack Hero

Remocon Bro's
KRBu-Remocon Bros

Remocon Bro's

"Gear Remocon! Funky! (Rhythmic beeping accompanied by steady rock music) Remote Control Gear!"
―Transformation announcement[src]


  • Height: 202.0 cm.
  • Weight: 103.5 kg.

Ability Perimeters:

  • Punching Power: 30.5 t.
  • Kicking Power: 37.2 t.
  • Maximum Jump Height: 48.6 m.
  • Maximum Running Speed: 100 m. per 1.7 sec.

One half of the Hell Bro's, Remocon Bro's (リモコンブロス Rimokon Burosu) is the turquoise Kaiser, transformed into by inserting Gear Remocon into the Nebulasteam Gun.

Remocon Bro's possesses strength to rival Kamen Rider Grease, Kamen Rider Cross-Z Charge, and Kamen Rider Build RabbitTank Sparkling Form, only beginning to struggle with Build's RabbitTank Hazard Form.

Remocon Bro's has 3 different finishers:

  • Nebulasteam Gun finisher:
    • Funky Drive (ファンキードライブ Fankī Doraibu): Remocon Bro's channels the power of a Gear and performs a powerful blast attack.
      • Gear Engine:
      • Gear Remocon: Remocon Bro's shoots energy gears at the enemy. This finisher can be accompanied with a Kaiser wielding the Steam Blade.
    • Funky Attack (ファンキーアタック Fankī Atakku) Remocon Bro's channels the powers of a Fullbottle and performs a powerful blast attack.
  • Nebulasteam Rifle finisher:
    • Funky Shot (ファンキーショット Fankī Shotto): Remocon Bro's channels the power of a Gear or Fullbottle and performs a powerful blast attack.
      • Gear Engine:
        • Elek Steam: Remocon Bro's shoots an electric energy-like engine bolt at the enemy.
      • Gear Remocon:
      • Bat: Remocon Bro's shoots a purple energy blast that detonates upon impact.

Appearances: ROGUE, Build Episodes 23-25, 29-32, 37-38

Hell Bro's
KRBu-Hell Bros

Hell Bro's

"Gear Engine! Gear Remocon! Funky Match! Fever! (Rhythmic beeping, engine revving) Perfect!"
―Transformation announcement[src]


  • Height: 202.0 cm.
  • Weight: 108.0 kg.

Ability Perimeters:

  • Punching Power: 41.6 t.
  • Kicking Power: 50.6 t.
  • Maximum Jump Height: 64.8 m.
  • Maximum Running Speed: 100 m. per 1.4 sec.

Hell Bro's (ヘルブロス Heru Burosu) is the fusion of Engine Bro's and Remocon Bro's, transformed into by inserting the Gear Engine or Gear Remocon into the Nebulasteam Gun, then removing it and inserting the other gear before pulling the trigger.

As Hell Bro's is a fusion of both Kaisers, Hell Bro's stats are higher than even Kamen Rider Rogue, with speed being similar to Build's Hazard Forms and average jumping power.

Hell Bro's has 3 different finishers:

  • Nebulasteam Gun finisher:
    • Funky Finish (ファンキーフィニッシュ Fankī Finisshu): Hell Bro's channels the power of a Gear and performs a powerful blast attack.
      • Gear Engine:
      • Gear Remocon:
    • Funky Attack (ファンキーアタック Fankī Atakku) Hell channels the powers of a Fullbottle and performs a powerful blast attack.
  • Nebulasteam Rifle finisher:
    • Funky Shot (ファンキーショット Fankī Shotto): Hell channels the power of a Gear or Fullbottle and performs a powerful blast attack.
      • Gear Engine:
      • Gear Remocon:

Appearances: Build Episodes 26-27, 29-32, 37-38




  • Steam Blade - Standard sidearm weapon. Can combine with the Nebulasteam Gun to form the Nebulasteam Rifle. Shared with Engine Bro's

Behind the Scenes


Fu Washio is portrayed by Osamu Adachi (足立 理). As Remocon Bro's, his suit actor is Kotaro Kaji (鍜治 洸太朗 Kaji Kōtarō).

As a teenager, he is portrayed by Shinta Takaiwa (高岩 芯泰 Takaiwa Shintai), son of veteran suit actor Seiji Takaiwa.


The Kanji that makes up Fu's first name (風) translates to "wind". This also explains the meaning behind his calm personality: "Calm like the wind".



Sento Kiryu - Ryuga Banjo - Kazumi Sawatari - Gentoku Himuro - Evolto - Nariaki Utsumi - Shinobu Katsuragi - Kengo Ino - Killbas
Transformation Gear
Fullbottles - Build Driver - Transteam Gun - (Great) Cross-Z Dragon - Sclashjellies - Sclash Driver - Hazard Trigger - Nebulasteam Gun - Cross-Z Magma Knuckle - Evol-Driver - Evol-Trigger - Grease Blizzard Knuckle
Drill Crusher - Hawk Gatlinger - 4Koma Ninpoutou - Kaizoku Hassyar - Fullbottle Buster - Steam Blade - Beat Closer - Twin Breaker - Muscle Glove - Solstall Wings - Giant Scratcher - Space Ride Arm - Spine Knuckle - Long Range Cleaner - Trash Converter - Gold Lio Gauntlet - Multi Deluge Gun
Pandora Box - Halfbodies - Fullbottle Holder - Build Phone
Vortex Finish - Hazard Level - Project Build - Sky Wall - Nebula Gas - Build Annihilation Plan
nascita: Misora Isurugi - Soichi Isurugi - Sawa Takigawa - Kazumi Sawatari - Gentoku Himuro
Prime Ministers: Taizan Himuro (Touto) - Yoshiko Tajimi (Hokuto) - Masakuni Mido (Seito)
Namba Heavy Industries Ltd.: Juzaburo Namba - Nariaki Utsumi - Guardian
Hell Bro's: Fu Washio - Rai Washio
Aliens: Vernage
Gentoku Himuro - Evolto - Nariaki Utsumi - Takumi Katsuragi - Shingo Kuwata - Eita Kawai
Touto: Needle Smash - Strong Smash - Burn Smash - Flying Smash - Mirage Smash - Square Smash - Press Smash - Ice Smash - Stretch Smash
Hokuto: Castle Hard Smash - Stag Hard Smash - Owl Hard Smash
Kaiser: Kaisei Mogami (World of Ex-Aid)
Kengo Ino - Ryoka Saiga - Mitsuomi Gohara - Evolto - Killbas