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Icon-build.png This article is about a character in Kamen Rider Build.

Soichi Isurugi (石動 惣一 , Isurugi Sōichi) is the 48-year-old father of Misora Isurugi and the owner of Café Nascita. He was an astronaut of the Kiwami Project who discovered the Pandora Box on Mars and subsequently became the host of Evolto, becoming Blood Stalk and later Kamen Rider Evol. After Evolto's defeat and the formation of the new world, Soichi returned to his former life as a cafe owner and simply Misora's father.



Soichi Isurugi is the father of Misora Isurugi and an astronaut working with the Kiwami Project. Ten years ago, Soichi was on a manned exploration on Mars and discovering the Pandora Box in the ruins. However, as he touched the relic, the extraterrestrial lifeform Evolto would take over his body and returned to Earth. To create the sixty Fullbottles from the Pandora Box based on Soichi memories, Evolto asks the man for thirty things he liked to create Biotic Bottles and odd objects to create the Abiotic Bottles.

Upon arriving on Earth, Evolto used Soichi's body to trigger the Pandora Box and raise the Pandora Tower. However, his attempt failed as Vernage also found her way to Earth and took hold of Misora's body to remove the essence of the Fullbottles, causing the Sky Wall to rise instead. After being medically diagnosed as being "psychologically insane", Soichi was arrested and placed in a mental hospital, in which Misora was also admitted into as well. Several months later, Evolto escaped from the mental hospital and took residence in Touto where he opened up a café called Nascita there.

Evolto continued to possess Soichi's body as he led Faust as Blood Stalk and posed as Sento Kiryu's mentor figure as he indoctrinated him to become Kamen Rider Build.

Release from Evolto

Sometime after Vernage made her presence, Soichi's consciousness was able to reemerge and trying to resist Evolto's hold over him. Soichi questioned Evolto's intentions before Evolto regained his control. He told Soichi not to do that again and to keep silent and watch as he transformed into Blood Stalk.

Soichi left unconscious.

When Evolto initiated "Phase 2" of his ultimate plan and possessed Ryuga Banjo, he had finally separate from Soichi Isurugi's body. Soichi was left unconscious and taken to a hospital by Sawa Takigawa and Kazumi Sawatari. After the Evol-Trigger was repaired and regained his Black Hole form, Evolto would later assume Soichi's appearance.

New World

Soichi confusing Sento with Taro Satou.

After Sento defeats Evolto for good, the new world had been successfully created. This new world version of Soichi now works at Nascita with his daughter. He's shown to actually be able to make a good cup of coffee, as proven by Sento, unlike Evolto's possession of him in the old world. Soichi mistakes Sento for Taro Satou, of the band Tsunagizu, and asks for his autograph. [The Tomorrow Build Will Create]

During the events of Build NEW WORLD: Kamen Rider Cross-Z, Misora mentions that her memories from the old world have returned but Soichi doesn't remember anything about the old world, since he was not being experimented on with Nebula Gas and his abilities was a result of Evolto taking over his body.


Ten years ago, Soichi was said to be a kind and caring person, as shown when he reads to his young daughter Misora Isurugi, remembering all the things she liked. According to Sawa's investigation of him, Soichi was also described to be someone who was friendly and had a strong sense of justice. However when he returned to Earth with Pandora's Box, he was possessed by Evolto. During his possession, Soichi was constantly struggling for control of his own body, although his attempts were in vain.

It's also implied that while Evolto is possessing Soichi, he would emulate Soichi's original personality.


Main article: Blood Stalk

Blood Stalk

Blood Stalk

Stalk's cobra head attack

Two giant Cobra projection.

"Cobra! Mist Match! Co-Co-Cobra! Cobra! Fire!"
―Transformation announcement[src]
  • Height: 201.5 cm.
  • Weight: 102 kg.

Ability Perimeters:

  • Punching power: 19 t.
  • Kicking power: 22.7 t.
  • Maximum jump height: 40 m.
  • Maximum running speed: 100 m. per 4.7 sec.

Similar to Night Rogue, Blood Stalk accesses his main form with the Transteam Gun and the Cobra Fullbottle. Unlike Riders and other Transteam/Kaiser system users, Evolto is almost always seen transformed into Blood Stalk after his identity has been revealed to Sento and the others at Nascita.

His stats are not only stronger than most of Build's forms, but also surpass Night Rogue's with only speed being slightly lower than his. Stalk also possesses numerous abilities built into his suit. On each wrist, he has extendable venomous tendrils that can shoot out and stab victims, injecting them with venom capable of either paralyzing, killing, or even disintegrating them. He can also create an energy cobra projection through his suit to attack or capture targets. It has been proven that Evolto is extremely proficient with the Blood Stalk arsenal and its abilities granted to him; his skill with the Transteam System, coupled with his enhanced durability, has allowed him to survive multiple skirmishes with Build and Cross-Z, and defeat Night Rogue in a duel.

The true purpose of the Blood Stalk system is to encourage the rise of Hazard Levels in Riders. Thus, he is shown capable of accepting far greater punishments than either Build or Cross-Z. Instead of showing pain or discomfort, Stalk is otherwise enjoying the beatings so long that his opponent's Hazard Level rises. In order to facilitate this, Blood Stalk can measure the current hazard level of Kamen Riders/Smash by simply touching them.

Stalk states that this form is merely temporary, as he uses powers acquired from Mars to stay toe to toe with enemies that are supposed to be stronger than what the Transteam System can put out. This is is shown when Stalk was able to fight on par with Build's RabbitTank Sparkling form while Night Rogue was easily defeated by it.

Blood Stalk also has several non-combat abilities. As mentioned by Takumi himself, Stalk's equipment has the ability to change its user's voice tone freely to hide his identity. It is later revealed that the alternate voice is that of Evolto. [The Truth of the Pandora Box]. Stalk is also able to activate the Guardians’ true programming as sleeper agents of Faust by snapping his fingers. When in need of a quick escape, he can escape any situation by becoming a cloud of red smoke and flowing away.

Blood Stalk consist of the following parts:

  • Blood Stalk Head (ブラッドスタークヘッド, Buraddo Sutāku Heddo): Blood Stalk's helmet.
    • Central Stalk (セントラルスターク, Sentoraru Sutāku): A chimney unit mounted on Blood Stalk's head. It has a heat removal function, a function to disperse toxic gas, and can also launch special bullets.
    • BS Side Blade (BSサイドブレード, BS Saido Burēdo): Data collection system in Blood Stalk's helmet. It collects data in real time, and performs emergency repair on damaged parts of the suit. It also manages the condition of the body.
    • Cobra Head Goggles (コブラヘッドゴーグル, Kobura Heddo Gōguru): Transparent goggles to protect Blood Stalk's face. The built in ultrasonic sensor allows him to fight in complete darkness.
    • Hide Seeker Eye (ハイドシーカーアイ, Haido Shīkā Ai): Blood Stalk's eyes. They It has a built in night vision sensor, and can detect heat sources and movement.
    • Air Face Duct (エアフェイスダクト, Ea Feisu Dakuto): A built in gas mask in the helmet. It removes harmful substances from the air when breathing and can discharge toxic gases.
    • BS Face Guard (BSフェイスガード, BS Feisu Gādo): Device that protects Blood Stalk's head. In response to an enemy's physical attack, it emits a wave that cancels out the impact to nullify the damage.
  • Cobra Chest Armor (コブラチェストアーマー, Kobura Chesuto Āmā): Blood Stalk's chest armor. The chest is equipped with a device called Steam Generator (スチームジェネレーター Suchīmu Jenerētā) that increases user's fighting ability. It can also accelerate the user's movement speed and attack power.
  • BS Unlimited Suit (BSアンリミテッドスーツ, BS Anrimiteddo Sūtsu): Shock resistant bodysuit of Blood Stalk. It can release the physical limiter and unleash the hidden physical ability of the user while offering protection from damage.
  • BS Cobra Shoulder (NRスチームショルダー, BS Kobura Shorudā): Blood Stalk's shoulder armor. They optimize arm movement to improve attack accuracy. A small plant is built inside to produce toxic gases and enhance the user's capabilities.
  • Venom Rush Arm (ヴェノムラッシュアーム, Vu~enomu Rasshu Āmu): Blood Stalk's arms. They increase speed and power, and can also use the attached needle Sting Viper (スティングヴァイパー, sutinguvu~aipā) to inject poison into enemies.
  • BS Cobra Glove (BSコブラグローブ, BS Kobura Gurōbu): Blood Stalk's gloves. They are reinforced, and have sharp claws at the fingers to allow for slashing attacks.
  • Metal Knee Bat (メタルニーバット, Metaru Nī Batto): Blood Stalk's knee pads. They optimize leg movement to improve speed.
  • Venom Rush Leg (ヴェノムラッシュレッグ, Vu~enomu Rasshu Reggu): Night Rogue's legs. They combine power and speed and specialize in high powered knees and continuous kicks.
  • Hide Seeker Shoes (ハイドシーカーシューズ, Haido Shīkā Shūzu): Blood Stalk's shoes. They suppress sound for stealth attacks, and can emit special steam for a kick attack.

With the Steam Blade or the Steam Rifle, he can use the following attacks:

  • Elek Steam (エレキスチーム, Ereki Suchīmu): Blood Stalk shoots electricity at the enemy.
  • Ice Steam (アイススチーム, Aisu Suchīmu): Blood Stalk performs an icy slash at the enemy causing them to freeze.
  • Devil Steam (デビルスチーム, Debiru Suchīmu): Blood Stalk fires a "steam" bullet which will home in on the target and inject them with a dose of Nebula Gas. When used on a human, the person will turn into a Smash; when used on a Smash, the Smash will grow to gigantic proportions and their host will lose all memories once freed.

Blood Stalk has 4 finishers:

  • Transtream Gun finishers:
    • Steam Break (スチームブレイク, Suchīmu Bureiku): Blood Stalk channels the powers of a Faust Fullbottle and performs a powerful blast attack.
      • Cobra: Blood Stalk shoots a purple energy ball that detonates upon impact.
    • Steam Attack (スチームアタック, Suchīmu Atakku): Blood Stalk channels the powers of a normal Fullbottle and performs a powerful blast attack.
  • Steam Rifle finishers:
    • Steam Shot (スチームショット, Suchīmu Shotto): Blood Stalk channels the powers of a Faust Fullbottle and performs a powerful steam blast attack.
      • Cobra: Blood Stalk shoot a purple cobra energy blast that detonates upon impact.
    • Steam Attack (スチームアタック, Suchīmu Atakku): Blood Stalk channels the powers of a normal Fullbottle and performs a powerful steam blast attack.
      • Rocket: Blood Stalk shoots a powerful blast attack that takes the form of a rocket. The rocket flies around the enemy before coming to the ground for an explosion.
Appearances: Build Episodes 3-14, 16-17, 19-21, ROGUE Episode 2, Raising the Hazard Level ~7 Best Matches~ ("Next Chapter", "Final Chapter"), Build 22-24, 28-34, 41 (flashback; archive footage only)

Guardian (Union State), red version

When multiple Guardians are combining into their larger battle robot form, the Guardian (Union State) (ガーディアン(合体状態), Gādian (Gattai Jōtai)), Blood Stalk can merge with it to become a red variant that he can control.

This form is exclusive toKamen Rider Build Episode 10

Main article: Kamen Rider Evol
Cobra Form (Phase 1)

Cobra Form

"Cobra! Rider System! Evolution! Are you ready? Cobra! Cobra! Evol Cobra! Fuhahahahahahahaha!"
―Transformation announcement[src]

Rider Statistics

  • Height: 195 cm.
  • Weight: 108 kg.

Ability Perimeters:

  • Punching power: 58 t.
  • Kicking power: 63 t.
  • Maximum jump height: 76.7 m.
  • Maximum running speed: 100 m. per 1.1 sec.

Cobra Form (コブラフォーム, Kobura Fōmu) is Evol's primary and default form accessed with the Cobra and Rider Evolbottles. Evolto labels this form as "Phase 1" (フェーズ1, Fēzu Wan).

As Evol, Evolto possesses tremendous power, as the Evol-Driver allows him to tap on the full power of the Pandora Box. His perimeters blow far past Grease, Rogue, and even Cross-Z Magma by a small margin. He also surpasses Build's RabbitRabbit and TankTank forms, though he loses to RabbitRabbit by maximum jump height and running speed, and TankTank by maximum kicking power.

Despite these small disadvantages, he still possesses abilities that are almost impossible to counteract, including teleportation and generating energy in his hand to perform an energy blast. He is also able to attack in extremely high speeds and block attacks quite easily, as shown during his first fight with Rogue.

His Evol Cobra Head (EVO-コブラヘッド, Ebo Kobura Heddo) contains the Xeno Head Armor (ゼノヘッドアーマー, Zeno Heddo Āmā) which strengthens its durability within each Phase. Between his EVO Twin Eye Cobra (EVOツインアイコブラ, Ebo Ai Kobura) lies the Master Planisphere (マスタープラニスフィア, Masutā Puranisufia), a device that allows him to determine which celestial body is his next target and formulate the suitable method of destroying it.[1]

In this form, Evol's armor parts are:[2]

  • EVO Cobra Shoulder (EVOコブラショルダー, Ebo Kobura Shorudā): A pair of shoulder armor that allows him to improve attack accuracy. Each has a built-in miniature plant that secretes toxic gases as enhancers of the user's ability.
  • Menace Rush Arms (メナスラッシュアーム, Menasu Rasshu Āmu): Evol's arms. Through an unknown substance that filled his suit, Evol's strength and speed are enhanced. By himself, Evol can manipulate a special aura that can move objects at will or detain his opponents.
  • EVO Xeno Vader Gloves (EVOゼノベイダーグローブ, Ebo Zeno Beidā Gurōbu): Enhanced combat gloves that allows him to create strong punches by manipulating nearby space.
  • Menace Rush Legs (メナスラッシュレッグ, Menasu Rasshu Reggu): Evol's leg units. Through an unknown substance that filled his suit, Evol's strength and speed are enhanced. By himself, Evol can manipulate a special aura that allows him to move objects or run at a tremendous speed.
  • EVO Xeno Vader Shoes (EVOゼノベイダーシューズ, Ebo Zeno Beidā Shūzu): Evol's combat shoes. Each can perform kick attacks by manipulating nearby space.
  • Xeno Chest Armor (ゼノチェストアーマー, Zeno Chesuto Āmā): Chhest armor which compresses and produces unknown substances within the Evolbottles. Said armor is stronger than any material on Earth and its durability increases within each Phase.
  • Armilla Reactor (アーミラリアクター, Āmira Riakutā): An Armillary sphere-themed conversion furnace which converts the unknown substance within Evolbottles into strong destructive energy. By completing all Phases, it can demonstrate its true ability.
  • EVO Omniverse Suit (EVOオムニバーススーツ, Ebo Omunibāsu Sūtsu): An enhanced battle suit that can emit blocking energy field, allowing Evol to protect himself from enemy attacks or carry out planetary destruction safely. It can also draw out the user's hidden ability and strengthen them based on the Phase.
  • EVO Material (EVOマテリアル, Ebo Materiaru): Golden armor parts on Evol's body. They can amplify Evolto's special abilities, empower wave attacks, generate annihilation poisons and allow warp teleportation.

Carried over from from Blood Stalk, Evol wields the Transteam Gun and Steam Blade in this form. He is also able to wield any of Build's weapons if he inserts the corresponding Fullbottle into the Evol-Driver along with the Rider Evolbottle.

This form has three finishers:

  • Evol Driver Finishers:
    • Evoltic Finish (エボルテックフィニッシュ, Eborutekku Finisshu) This finisher has two variations:
      • Rider Kick: Evol generates an energy star map beneath his feet that then transforms into a dark red and dark blue energy galaxy that flows into his right foot before delivering an explosive kick.
    • Steam Shot (スチームショット, Suchīmu Shotto): Evol channels the powers of a Evolbottle/Fullbottle and performs a powerful steam blast attack.
      • Cobra Evolbottle
        • Elek Steam: Evol shoots a red and blue homing shot coated in electricity
Appearances: Build Episodes 33-34, 40-41



  • Transteam Gun - Blood Stalk's transformation device and personal weapon. Evol inherits it as his personal weapon
  • Fullbottles - Blood Stalk's transformation trinkets. Used by Evol to summon weapons and perform finishers.
  • Evol-Driver - Evol's transformation device
  • Evolbottles - Evol's transformation trinkets
  • Evol Trigger - Evol's upgrade device for Black Hole form


  • Steam Blade - Blood Stalk's standard sidearm weapon. Can combine with the Transteam Gun to form the Steam Rifle. Continued to be used by Evol.
  • Drill Crusher - Evol's personal weapon in Rabbit Form
  • Hawk Gatlinger - Evol's weapon granted by the Gatling Fullbottle

Behind the Scenes


Soichi is portrayed by Yasuyuki Maekawa (前川 泰之, Maekawa Yasuyuki). As Evolto, his other voice was voiced by Tetsuo Kanao (金尾 哲夫, Kanao Tetsuo), who previously voiced Namakelder in Happiness Charge Pretty Cure!. As Blood Stalk and Kamen Rider Evol, his suit actor is Kazuya Okada (岡田 和也, Okada Kazuya).


The katakana "sutāku" (スターク) in his name is usually translated as "Stark". The name "Stark" in Blood Stark can also be "Stalk" and "Stalker".


  • As a hint to Stalk's true identity as Soichi, the collar on Blood Stalk's suit was modeled after the collar of a space suit.[3]




Icon-build.png Kamen Rider Build
Kamen Riders
Sento Kiryu (Takumi Katsuragi) - Ryuga Banjo - Kazumi Sawatari - Gentoku Himuro - Evolto - Nariaki Utsumi - Shinobu Katsuragi
Movie-exclusive: Kengo Ino - Killbus - Keiji Uraga
Drivers/Transformation Gear
Build Driver - Transteam Gun - Nebulasteam Gun - Sclash Driver - Evol-Driver
Build Driver Adapters
(Great) Cross-Z Dragon - Hazard Trigger - Cross-Z Magma Knuckle - Evol-Trigger - Grease Blizzard Knuckle - Killbuspider - Grease Perfect Kingdom
Normal Weapons
Drill Crusher - Hawk Gatlinger - 4Koma Ninpoutou - Kaizoku Hassyar - Fullbottle Buster - Steam Blade - Beat Closer - Twin Breaker
Suit-Equipped Weapons
Muscle Glove - Solstall Wings - Giant Scratcher - Space Ride Arm - Spine Knuckle - Long Range Cleaner - Trash Converter - Gold Lio Gauntlet - Multi Deluge Gun
Collectible Devices
Fullbottles - Sclashjellies
Fullbottle-related Devices
Fullbottle Holder - Pandora Box - Build Phone - Halfbodies
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
Normal Smash: Fang Smash - Needle Smash - Strong Smash - Burn Smash - Flying Smash - Mirage Smash - Square Smash - Press Smash - Ice Smash - Stretch Smash
Empowered Smash: Strong Smash Hazard - Press Smash Hazard - Stretch Smash Hazard - Flying Smash Hazard
Hard/Hazard Smash: Castle Hard/Hazard Smash - Stag Hard/Hazard Smash - Owl Hard/Hazard Smash
Clone Smash: Press Clone Smash - Stretch Clone Smash - Strong Clone Smash - Flying Clone Smash
Lost Smash: Owl Lost Smash - Stag Lost Smash - Castle Lost Smash - CD Lost Smash - Scissors Lost Smash - Zebra Lost Smash
Foundation X
Kaisers: Kaisei Mogami (World of Build, World of Ex-Aid) - Nebula Bugster
Blood Tribe
Kengo Ino - Ryoka Saiga - Mitsuomi Gobara - Evolto - Killbus - Akaba (imitation) - Aoba (imitation) - Kiba (imitation) - Remocon Bro's (imitation) - Engine Bro's (imitation)
Down Fall
Keiji Uraga - Simon Marcus (Phantom Crusher)