The Unstoppable Hazard

is the twenty-first episode of Kamen Rider Build. This episode is a continuation of Build Rabbit Tank Hazard's debut from the previous episode, resulting in the death of Aoba.
==Synopsis==
Fighting with the forbidden item, the Hazard Trigger, has transformed Sento into a dark version of Build, known as a “Hazard Form”. If he continues to fight using the Hazard Trigger, according to Katsuragi’s words, he will lose his sense of self. Sento is using the same technology the enemy has been using on himself! But Build loses consciousness during the fight. And then, Build stands before the Hokuto Trio as he decides to finish his fight against them…
==Plot==
to be added
==Cast==
*: 
*: 
*: 
*: 
*: 
*: 
*: 
*: 
*: 
*: 
*: 
*: 
*: 
*: 
===Guest Casts===
*: 
*TV Announcer: 
*Ring Announcer: 
===Suit Actors===
*Kamen Rider Build: 
*Kamen Rider Cross-Z Charge: 
*Kamen Rider Grease: 
*Blood Stalk: 
*Castle Hazard Smash: 
*Stag Hazard Smash: 
*Owl Hazard Smash: 
==Forms and Collectibles Used==
===Fullbottles===
*Bottle used:
**Build
***Biotic: Rabbit, Phoenix, Rose, Turtle
***Abiotic: Tank, Soujiki, Helicopter, Watch
***Other: Hazard Trigger
**Grease
***Biotic: N/A
***Abiotic: Lock (In Sclash Driver)
**Blood Stalk
***Biotic: Cobra
***Abiotic: N/A
**Castle Hazard Smash
***Castle
**Stag Hazard Smash
***Kuwagata
**Owl Hazard Smash
***Fukurou
*Form used:
**Build
***RabbitTank Hazard Form, PhoenixSoujiki Form, RoseSoujiki Form, RoseCopter Form, TurtleWatch Form (off-screen), RabbitTank Form
===Sclashjellies===
*Jelly used:
**Cross-Z Charge
***Dragon
**Grease
***Robot
==Errors==
*Before activating RoseCopter, the Rose Fullbottle is set back into the Driver as if Build didn't assume RoseSoujiki and the Snap Ride Builder part for the Rose Halfbody wasn't clear.
==Notes==
*As part of Super Hero Time, this episode aired alongside episode 48, . Starting on February 11, 2018, will join Build in Super Hero Time block.
*Viewership: 3.5%
*Formula of the title:\arg_{n}\max[\forall x \exists\iota\leq n,x+\iota\not\in\{harshad\}]=21 ()
*Fullbottles Obtained: Rose, Unicorn, Turtle, Kabutomushi, Spider, Tora, Kujira, Kirin, Hachi, Helicopter, Watch, Camera, Reizoku, UFO, Jet, Senpuki
*Closing Screen Fullbottles & Sclashjellies:
**Kamen Rider: Build
**Fullbottles:
***Biotic: Rose
***Abiotic: Helicopter
*Count at episode end
**Bottles in Build's possession:
***Biotic: Rabbit, Taka, Panda, Kaizoku, Phoenix, Wolf, Unicorn, Rose, Turtle, Kabutomushi, Kuma, Dog, Spider, Tora, Kujira, Shika, Kirin, Penguin, Obake, Hachi, Sai
***Abiotic: Tank, Gatling, Rocket, Syoubousya, Densya, Light, Robot, Smapho, Keshigomu, Helicopter, Watch, Camera, Televi, Mic, Reizoku, UFO, Jet, Pyramid, Senpuki, Sukebo, Magnet, Sensuikan, Dryer
***Other: RabbitTank Sparkling
**Bottles in Cross-Z Charge's possession:
***Biotic: Dragon
***Abiotic: Lock
***Other: Cross-Z Dragon
**Bottles in Grease's possession: Kuwagata
**Bottles in Night Rogue's possession: Bat
**Bottles in Blood Stalk's possession:
***Biotic: Cobra, Gorilla, Ninjya, Harinezumi, Lion, Octopus, Same
***Abiotic: Diamond, Comic, Soujiki, Bike
**Bottles in Castle Hazard Smash's possession: Castle
**Bottles in Owl Hazard Smash's possession: Fukurou
**Jellies in Cross-Z Charge's possession: Dragon
**Jellies in Grease's possession: Robot
*In the opening sequence for this episode:
**Grease replaces the scene with two of Build's forms.
**Cross-Z Charge replaces the scene with Cross-Z.
**Build changing from RabbitTank to RabbitTank Sparkling replaces the scenes with GorillaMond and HawkGatling.
*The title of the episode has two meanings:
**Hazard form is unstoppable, the power of Hazard Form is too strong that it cannot be stopped by others
**Hazard form will not stop fighting, Sento cannot control Hazard Form to stop it from destroying every enemy
*When Sento revisits the location of Aoba's death, the flowers he places there are purple hyacinths. Purple hyacinths are a symbol of sorrow, as well as asking for forgiveness.
*When Isurugi presents Sento the case of Fullbottles, despite being on Seito- and Hokuto-colored Panels, the assorted Bottles are not arranged by district, Best Match, or even biotic/abiotic. This may either be an error by the prop department or be Isurugi trying to make Sento find the Matches on his own.
*This is the first episode since it's debut that Sento does not assume his RabbitTank Sparkling Form.
*This episode showcases the debut of Build's RoseCopter Form and RoseSoujiki Trial Form, and the Unicorn, Turtle, Spider, Kabutomushi, Tora, Kujira, Kirin, Hachi, Same, Watch, Reizoko, Camera, UFO, Jet, and Senpuki Fullbottles, as well as a tease of Build's TurtleWatch Best Match. 
==DVD/Blu-ray releases==
*Kamen Rider Build Volume 6 features episodes 21-24: The Unstoppable Hazard, Victory of Tears, The Phantom of the West and A Man Called Rogue.
*Blu-ray Collection 2 comes with 12 episodes.
Build Vol. 6.jpg|Kamen Rider Build Volume 6, DVD
91R ZCOJk0L. SL1469 .jpg|Kamen Rider Build Collection 2, Blu-ray
==External links==
*TV Asahi's official episode guide for ハザードは止まらない.
*Toei TV's official episode guide for ハザードは止まらない
==References==
Category:New Form Episode