Kyoichi Shimizu is one of the victims of Faust's experiments who was turned into the Strong Smash. His Smash essence was used as the basis for the Gorilla Fullbottle. He later uses the Kuwagata Fullbottle to become the Stag Lost Smash.
Shimizu was present during Ryuga Banjo's escape from Faust's experiment, recognized by his signature dragon-shaped ear decoration, later being turned into the Strong Smash. The Strong Smash appeared and attacked Sento Kiryu and Ryuga, grabbing Ryuga and trying to take him away, presumably back to the facility. Ryuga fought back without success, but Sento transformed into Kamen Rider Build RabbitTank and fought it. He briefly took HarinezumiTank before returning to RabbitTank and defeating the Smash with Vortech Finish, extracting the Smash essence with a blank Fullbottle. Questioned by Ryuga, Shimizu claimed to remember nothing, escaping into some tall grass as a squad of Touto Guardians arrived.
Publication Information
- Build : Kyoichi Shimizu
- Japanese : 志水恭一
- Version : Kamen Rider Build
- Alter Ego : Shimizu
- Type : Faust's Experiments Subject
- Relative :
- Affiliation : Smash
- Gender : Male
- Origin : Earth (World of Build)
- Season : Kamen Rider Build
- First Appearance : Kamen Rider Build Episode 1 : That One with the Best Match
- Last Appearance :
- Number of Appearances :
- Potrayer : Shohei Yamazaki
- Main View : Full Episod

The Bottle was later purified into the Gorilla Fullbottle. Later, presumably under Evolto command, Shimizu encounter Sento and by using Kuwagata Lost Fullbottle, he becomes Kuwagata Lost Smash and attacks Sento. Sento later cancels his transformation using Build Genius form. However, just before Shimizu leaks more info about Katsuragi Shinobu, Evolto kills him by injecting Shimizu with a lethal dose of poison that disintegrates him.
Forms
Strong Smash Hazard

- Main Articles : Strong Smash Hazard
- Origin : Earth
- Version : Kamen Rider Build Series
- Type : Smash
- Alter Ego : Kyoichi Shimizu
- Form : Strong Smash Hazard
- Height : 207.1 cm
- Weight : 109.1 kg
- Appearances : Build Episode 1
- The first Smash form Shimizu took after being exposed to Nebula Gas by Faust.
- The Strong Smash wields vast physical strength, seen when it knocked a car several meters away with one punch.
- The Strong Smash can also jump very high into the air.

- Main Articles : Stag Lost Smash
- Origin : Earth
- Version : Kamen Rider Build Series
- Type : Smash
- Alter Ego : Kyoichi Shimizu
- Form : Stag Lost Smash
- Height : 205.2 cm
- Weight : 124.4 kg
- Appearances : Build 41
- Shimizu transforms into the Stag Hard Smash by using the Kuwagata Fullbottle and absorbing two Clone Smash.
- The Stag Lost Smash is armed with the pair of sword-like Rapture Scissors.
- The Stag Lost Smash can move at super speed.
Kuwagata Lost Fullbottle

- Kuwagata Lost Fullbottle
- Kuwagata Lost Fullbottle, used by Kyoichi Shimizu to transform into the Stag Lost Smash.
Unidentified test subject

Publication Information
- Build : Unidentified test subject
- Japanese :
- Version : Kamen Rider Build Series
- Known as :
- Type :
- Summoned by Evolto (Ryuga Banjou)
- Flying Clone Smash
- Affiliation : Smash
- Gender : Male
- Season : Kamen Rider Build
- First Appearance : Kamen Rider Build Episode 36 : Evolto Hunts the Stars
- Last Appearance :
- Number of Appearances :
- Potrayer :
- Main View : Full Episod
Flying Clone Smash

- Main Article : Flying Clone Smash
- Origin : Earth (World Of Build)
- Version : Kamen Rider Build
- Type : Smash
- Form : Flying Clone Smash
- Host : Unidentified test subject
- Height : 202.5 cm
- Weight : 105.5 kg
- Appearances : Build Episode 36, 41, 45
- An artificial copy of a Smash not requiring a test subject, even stronger than the Flying Smash Hazard. Though lacking intelligence, it does not feel pain and will continue fighting until destroyed