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

―Blood Stalk's transformation catchphrase.[src]

"I'm the game maker. I derive the best strategy by considering every possibility. Everything is going as planned."
―Blood Stalk's speech to Night Rogue[src]

"I am Blood Stalk...*clearing throat*...or do you prefer this voice better?"
―Souichi's introduction as Blood Stalk while demonstrating his voice changer function.[src]

Soichi Isurugi (石動 惣一 Isurugi Sōichi) is the father of Misora Isurugi, the owner of the café nascita and also the host of Evolto.

Later, Evolto, in Soichi's body, uses the Evol-Driver to become Kamen Rider Evol.

Character History

Early Life

Ten years prior to the events of Build, Soichi was an astronaut working with the Kiwami Project, discovering the Pandora Box on Mars. However finding the box would change his mentality, which he jokingly admitted that it "did a number on his mind". In truth, it was Evolto who had somehow possessed Soichi's body and fled with him to Earth, unknown to anyone.

Returning to Earth

Main article: Evolto

Release from Evolto

When Evolto initiated "Phase 2" of his ultimate plan and possessed Ryuga Banjo, Soichi was left unconscious and taken to a hospital by Misora and Kazumi Sawatari. Tower of Destruction After the Evol-Trigger was repaired and regained his Black Hole form, Evolto (now a corporeal shape-shifter) would later assuming Soichi's appearance. Mad World


Ten years ago, Soichi was said to be a kind and caring person. However, upon his first exposure to the Pandora Box's energy, Soichi was transformed into a ruthless, cunning mastermind due to possession by Evolto.

It is later shown, however, that he is struggling for control, trying to fight back against Evolto, though these are vain attempts as Evolto has complete control over his body.


Main article: Blood Stalk

Blood Stalk
KRBu-Blood Stark

Blood Stalk

Stalk Cobra attack

Stalk's cobra head attack

BS Snakes

Two giant Cobra projection.

"Cobra! Mistmatch! Co-Cobra... Cobra... Fire!"
―Transformation announcement[src]
  • Height: 201.5 cm
  • Weight: 102.0 kg

Ability Perimeters:

  • Punching power: 19.0 t
  • Kicking power: 22.7 t
  • Maximum jump height: 40.0 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.

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 shoot 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, 28-33

Red Guardian Union (damaged)

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.

Appearances: Build Episode 10

Main article: Kamen Rider Evol
Cobra Form (Phase 1)
KRBu-Evolcobra Phase1

Cobra Form

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

Rider Statistics

  • Height: 195.0 cm
  • Weight: 108.0 kg

Ability Perimeters:

  • Punching power: 58.0 t
  • Kicking power: 63.0 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 entitled this form "Phase 1" (フェーズ1 Fēzu Wan).

As Evol, Soichi/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 punching power and 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 Plani Sphere (マスタープラニスフィア Masutā Purani Sufia), a device that allows him to determine the which celestial body is his next target and formulate the suitable method of destroying it.[1]

In this form, Evol's armor parts are:

  • 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.[2]
  • 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.[3]
  • 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.[4]
  • 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.[5]
  • 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.[6]
  • 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.[7]
  • 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.[8]
  • 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.[9]
  • 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.[10]

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

This form has two 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.
      • Rider Punch: Evol delivers a flaming punch.
  • Steam Rifle Finishers:
    • 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



  • 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".


  • Soichi has the habit of saying out "Objection!" (異議あり! Igiari!) before voicing his comments. The style and tone used as he delivers the phrase is reminiscent of the same iconic phrase from the Ace Attorney game series.
  • Being a proprietor of a café where the main hero works and/or frequents in their spare time brings to mind Tōbei Tachibana and Kiyojiro Bando.
  • Blood Stalk's cobra motif, along with Night Rogue's bat motif, is part of the recurring bat/cobra/spider trio in the Kamen Rider franchise, a tribute to the first two Shocker monsters as well as the first monster to be upgraded.
    • Same as Night Rogue, Blood Stalk's transformation catchphrase, "Jōketsu" (蒸血), is also a homage to Space Sheriff GavanIcon-crosswiki and Space Sheriff ShaiderIcon-crosswiki's catchphrase ("Jouchaku" and "Shouketsu")
  • He's similar to DJ Sagara from Kamen Rider Gaim, as he was initially a supporting character but is later revealed to be the mastermind behind everything, and is snake-themed.
    • An inversion of their backgrounds, while DJ Sagara wanted to encourage growth and improvement of all species across the universe, being a passive observer to the results, Soichi does so to improve the already powerful and only while they remain useful to him, becoming directly involved to make it happen.
  • 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.[11]
  • The CGI model of Blood Stalk's Energy Cobra is a reuse of part of Kamen Rider Ouja's Venosnaker.