This article is about a/an transformation equipment in Kamen Rider Build.

"Hazard On! (Rock music)"
―Activation announcement[src]

"(Biotic Fullbottle name)! (Abiotic Fullbottle name)! Super Best Match!"
―Super Best Match announcement via the Build Driver [src]

"Don Ten Kan! Don Ten Kan!"
―Looping standby announcement via the Build Driver[src]

"Gata Gata Gotton! Zuttan Zutan!"
―Vortex Crank cranking announcement via the Build Driver[src]

"Are you ready? Uncontrol Switch! Black Hazard! Yabei!"
―Hazard Form transformation announcement[src]

"Ready, go! Hazard Attack!"
―Hazard Form charged attack announcement[src]

"Max Hazard On!"
―Max Hazard Mode activation announcement[src]

"Ready, go! Overflow! Yabei!"
―Overflow mode announcement[src]

"Ready, go! Hazard Finish!"
―Hazard Form finisher announcement[src]

"(Fullbottle insertion announcement) Build up! Are you ready? Overflow! (Fullbottle jingle) Yabei! (Fullbottle ending phrase)"
―Transformation announcement with a Fullbottle that occupies both slots[src]

"Ready, go! Hazard Finish! (Fullbottle finisher announcement)"
―Finisher announcement with a Fullbottle that occupies both slots[src]

The Hazard Trigger (ハザード トリガー Hazādo Torigā) is a turbocharger-like device compatible with the Build Driver, created with the primary function of serving as a method to destroy Evolto. It is primarily used by Kamen Rider Build to upgrade any Best Match form into a Super Best Match (スーパベストマッチ Supā Besuto Matchi), creating a Hazard Form. Used this way within the Super Best Match, Kamen Rider Build runs the risk of losing control of himself and going on a destructive rampage.

The FullFull RabbitTank Bottle was created for use with the Hazard Trigger, transforming Build into RabbitRabbit Form or TankTank Form, which are more powerful than standard Hazard Forms and do not come with the risks. The Hazard Trigger has also been used to directly increase the power of Kamen Rider Cross-Z Magma and Kamen Rider Build Genius Form, and it is used by Kengo Ino and Keiji Uraga to transform into Kamen Rider Blood and Kamen Rider Metal Build respectively.

The creation of the Hazard Trigger is categorized as File XXX in Project Build.


The Hazard Trigger is composed of the following parts:

  • The Force Ride Meter (フォースライドメーター Fōsu Raido Mētā) is located at the centre of the Hazard Trigger. It measures the fighting ability of the user, and the higher the reading, the more powerful the attacks are. However, if the meter reaches the dangerous zone during battle, the user will go beserk due to massive amounts of stimuli, causing a loss of sense of self.
  • The Progress Tank (プログレスタンク Puroguresu Tanku) is the handle sticking out of the Hazard Trigger. It is filled with an enhancement agent named Progress Vapor (プログレスヴェイパー Puroguresu Veipā), a reinforcement agent developed from Nebula Gas components, and has the ability to raise Hazard Levels. This agent reacts with Transgel Solid inside of Fullbottles and turns them into metallic components, During transformation, the Progress Vapor is poured through the Hazard Ride Builder (ハザードライドビルダー Hazādo Raido Birudā)( an injection mold-like contraption) and processed into reinforced equipment along with the contents of the Fullbottles, creating the Hazard Suit.
  • The BLD Ride Connector (BLDライドコネクター BLD Raido Konekutā) is the grey part sticking out of the bottom of the Hazard Trigger. It connects the trigger to the BLD Ride Port (BLDライドポート BLD Raido Pōto) top of the Build Driver. Responsible for developing the Hazard Ride Builder.
  • The Security Clear Cover (セキュリティクリアカバー Sekyuriti Kuria Kabā) conceals the BLD Hazard Switch, preventing accidental pressing during battle.
  • The blue button on the Hazard Trigger is known as the BLD Hazard Switch (BLDハザードスイッチ BLD Hazādo Suitchi'), which is used to activate the switch itself before use. Once transformed, pressing it again puts the Hazard Trigger in Max Hazard Mode.


"Like I thought, they went out of control. Wanna know how you can stop their power? The forbidden item created by Katsuragi... the Hazard Trigger."
―Blood Stalk revealing the Hazard Trigger to Sento[src]

The Hazard Trigger, dubbed the "forbidden item" by its creator Takumi Katsuragi, can massively boost the Hazard Level of its user, with deadly side effects. Attached to the Build Driver, it upgrades Kamen Rider Build's standard two-Fullbottle forms into Hazard Forms, granting him great strength. However, after several minutes in a Hazard Form, Build will experience a stimuli overload, causing him to lose consciousness and go on a mindless rampage, attacking anything in his path. The Hazard Trigger can be used to permanently upgrade a Smash, but they will die upon defeat.

According to Soichi Isurugi, a user can prolong the stimuli overload if their Hazard Level is high enough prior to using it, as proven in Episode 35. After Sento creates the FullFull RabbitTank Bottle, he upgrades the black Hazard Form into RabbitRabbit Form and TankTank Form, which not only supresses the stimuli overload, but also boosts Build's powers massively and then some. The Genius Fullbottle also has been proven to be a successful suppressant as well, although Build will simply go into Genius Form. This method will only work for as long as the FullFull Bottle (or Genius Bottle) stays attached to the Driver, otherwise Sento will revert back into the black Hazard Form and the side effects will return after a certain amount of time as passed.

To access Hazard Forms, the BLD Hazard Switch is pressed before attaching the Hazard Trigger to the Build Driver above the Vortex Charge. The Build Driver is then used normally, triggering a transformation into a Hazard Form instead of a normal Best Match form. The Devil's Trigger While in a Hazard Form, the Build Driver's Vortex Lever can be cranked again to trigger the Hazard Attack (ハザードアタック Hazādo Atakku) finishing move. Pressing the BLD Hazard Switch again to trigger Max Hazard mode and turning the Vortex Crank of the Build Driver will allow Build to access Overflow (オーバーフロー Ōbāfurō) Mode, raising both his Hazard Level and fighting ability, which is potent enough to inflict fear upon both enemy and ally alike. Upon entering Overflow Mode, turning the Vortex Crank a second time will allow Build to perform the Hazard Finish (ハザードフィニッシュ Hazādo Finisshu).

With the Hazard Trigger in Max Hazard Mode, the FullFull RabbitTank Bottle can be inserted into the Build Driver to upgrade RabbitTank Hazard Form into either RabbitRabbit Form or TankTank Form. In these forms, the Hazard Finish is upgraded into the RabbitRabbit Finish (ラビットラビットフィニッシュ Rabitto Rabitto Finisshu) or the TankTank Finish (タンクタンクフィニッシュ Tanku Tanku Finisshu). The Counterattack Hero

To permanently upgrade a Smash into a Hazard Smash, the Hazard Trigger is hooked up to a special machine which the subject will lie in to be infused with the Hazard Trigger's power. The Forbidden Item

After Build assumes Genius Form, the Hazard Trigger can be used in conjunction with the Genius Fullbottle to purify Lost Fullbottles without having to go on a destructive rampage. The Scientist of Hope


Temporarily overriding Ryuga's free will, "Kengo Ino" of the Blood Tribe had him attack Sento and rob him of the Hazard Trigger, which Ryuga provided to him. Using it in the Build Driver taken from Ryuga with the Great Cross-Z Dragon and Cobra Lost Fullbottle, "Kengo" assumed the form of Kamen Rider Blood. Ultimately, however, the Hazard Trigger was returned to Sento among the rest of the appropriated gear when he and Ryuga defeated Blood as Kamen Rider Cross-ZBuild. Kamen Rider Build: Be The One



  • Rider Punch: Build transfers surplus Nebula Gas into his HZ Deadly Gloves and delivers a powerful punch, summoning a wolf-like energy projection which "bites" down on the enemy.

  • KaizokuRessya: Build repeatedly punches the enemy with his HZ Deadly Gloves delivering purple shockwaves on impact.

  • Rider Kick: This finisher has two variations:
    • Build release an electricity from his HZ Deadly Glove to paralyze the enemy, then coats his right HZ Vanish End Shoe in purple, dark energy before delivering a powerful side kick.
    • Build rushes towards the enemy and performs a flying kick.

  • Rider Shooting: Build traps the enemy in a black cloud and performs a series of purple blasts with the Hawk Gatlinger.

  • Metal Build performs a roundhouse kick motion towards the opponent, creating a tank track that flies into the target and grinds against them, acting like a chainsaw. This attack can strike multiple opponents.

  • Phantom Build launches a volley of missiles from his back before performing two consecutive roundhouse kicks towards the opponent, creating a tank track that flies into the target.

  • Hazard Attack (ハザードアタック Hazādo Atakku): Metal Build jumps into the air before crashing into the target with a double knee drop. He then created an energy tank tread that grinds the enemy into the ground.

  • RabbitRabbit Finish (ラビットラビットフィニッシュ Rabitto Rabitto Finisshu): Jumping into the air, Build stretches his leg towards the opponent, and pulling his body towards his foot, connects with the target, with the resulting impact sending his opponent flying.

  • Genius Finish (ジーニアスフィニッシュ Jīniasu Finisshu): Build delivers a punch that creates a swirling, rainbow-colored shockwave upon impact. With the effect of Hazard Trigger, he gains the ability to negate the Pandora Panel's effects on Lost Fullbottles.

  • Volcanic Finish (ボルケニックフィニッシュ Borukenikku Finisshu): Cross-Z Magma performs an enhanced version of his original Volcanic Finish. With the effect of the Hazard Trigger, he can overpower Evol's Black Hole Form for a short period of time.


  • Being a non-collectible device that can be slotted into the main Rider's Driver to access an upgrade recalls the Genesis Driver's Core Unit that can be attached into the Sengoku Driver.
    • While it does not replace any portion of the Build Driver, it does possess the same process of modifying the "armor". However, the difference of each form is seen in the visor as the modified armor retains the same design for any form using the Hazard Trigger, with the suit's design appearing more symmetrical; similar to the Jimber Arms forms accessed by the Sengoku Driver.
      • The only other devices that impact the basic design of the suit are the Cross-Z Dragon adapter due to using one Fullbottle for the transformation, and the Cross-Z Magma Knuckle for the same reason, except its use completely alters the base suit.
        • The result of transfroming with the Grease Blizzard Knuckle appears as a fusion of the Robot Halfbody and the suit and helmet design of Kamen Rider Grease's Sclash Driver form, but colored differently, with the shoulder pads displaying the symbols of Grease on one and the Hokuto Sanbagarasu' Fullbottle designs on the other.
      • It would later be enhanced with the FullFull RabbitTank Bottle, forming additional armor over the Hazard Suit.
  • The aspects of being a "Forbidden Device" and being used in response to the enemy's increasing power are shared with the Armed Saber from Kamen Rider Hibiki.
    • The comparison is further emphasized by how its combination with the FullFull RabbitTank Bottle provides additional armor as a similar indication that the form is now usable by the Rider.
  • Its impact on the Rider Form's appearance and the risk of causing volatile behavior are reminiscent of the Fang Memory from Kamen Rider W. Both devices are also used to access their titular rider's super forms.
    • A key difference is that, while FangJoker's control is dependent on the user's compatibility with the Joker Memory, indicated by a novel, Hazard Forms only require a high Hazard Level to neutralize the side effect. This has been exemplified by weapon-wielding Super Best Matches, as opposed to the unseen half changes with the Fang Memory possessing either the Metal Shaft or the Trigger Magnum.
      • While there are weapon-wielding Hazard forms, the general aspect of the finishers tend to parallel the finisher of FangJoker, where the device is utilized first to initiate the finisher and/or the finisher being an extension of the Form(Use of the HZ Vanish End Shoes/HZ Deadly Gloves and the Maximum Saber, respectively).
      • In the Futo Detective Manga, there was evidence that half changes with the Fang Memory can still produce finishers geared towards usage of the fang-based weapons, further paralleling with Hazard forms being more focused on the energy produced by the Hazard Trigger.
  • The Hazard Trigger's negative effects on its user's mental state are similar to the Sclash Driver's, although the Hazard Trigger's effects are much more dangerous and uncontrollable.
    • Unlike other forms that cause Riders to go berserk, the Hazard Trigger's effects are not wild and aimless; the user loses all awareness of anything except the urge to destroy, and will fight with all their skills and no mercy.
  • Hazard Form's upgrade with the FullFull RabbitTank Bottle appears as an inverse of Kuuga's Forms, where as Rising Mighty becomes Amazing Mighty by enhancing a colored Upgrade Form into a singular, black Super Form, Hazard Form gains two distinctly colored Super Forms by adding new armor to the black Hazard Suit.
    • The additional armor is similar to the Gamers for Levels 3 and onward from Kamen Rider Ex-Aid where it depicts the theme of the form before merging with the Rider.
    • The design of the armor pieces seem to stem from the shoes of the respective Half Body, noticeably with the red arrows found on the "cuff" of the Rabbit Foot Shoes being applied to both ends of the Dimension Springers and the Tank Roller Shoes being more emphasized as the Blue Tank Rollers.


See Also


Sento Kiryu (Takumi Katsuragi) - Ryuga Banjo - Kazumi Sawatari - Gentoku Himuro - Evolto - Nariaki Utsumi - Shinobu Katsuragi
Movie-exclusive: Kengo Ino - Killbus - Keiji Uraga
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 - Killbuspider - Grease Perfect Kingdom
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
nascita: Misora Isurugi - Soichi Isurugi - Sawa Takigawa - Kazumi Sawatari - Gentoku Himuro
Kamen Riders: Eiji Hino - Gentaro Kisaragi - Kouta Kazuraba - Takeru Tenkuji - Emu Hojo - Hiiro Kagami - Taiga Hanaya - Kiriya Kujo - Kuroto Dan - Parado - Sougo Tokiwa - Geiz Myokoin - Tsukuyomi
Prime Ministers: Taizan Himuro (Touto) - Yoshiko Tajimi (Hokuto) - Masakuni Mido (Seito)
Namba Heavy Industries Ltd.: Juzaburo Namba - Nariaki Utsumi - Haruhiko Wanibuchi - Guardian
Hell Bro's: Fu Washio - Rai Washio - Yoshikazu Takahashi - Norio Matsui
Aliens: Vernage
Gentoku Himuro - Evolto - Nariaki Utsumi - Takumi Katsuragi - Shingo Kuwata - Eita Kawai - Yoshikazu Takahashi - Norio Matsui
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 Gobara - Evolto - Killbus
Keiji Uraga - Simon Marcus (Phantom Crusher)
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