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

Shiro Mizuki (水城 史朗 Mizuki Shiro) is the human alter-ego of Kamen Rider G4 (仮面ライダーG4 Kamen Raidā Jī Fō, Masked Rider G4), a Rider who only appeared in Kamen Rider Agito: Project G4.


He was one of the military personnel guarding the GA psychic educational facility during the time it was attacked by the Formica Pedes. Though he would survive the ordeal, he would be left a jaded man.

With his pride as a soldier shattered, Mizuki began living as one who would embrace death as the true means of becoming stronger. He would eventually volunteer as the operator for the G4 exo-suit and, as fate would have it, clash with G3-X operator Hikawa, to put their ideals to the test on the battlefield. But throughout the course of the battle, the G4 begins to suffer malfunctions.

Despite this, Mizuki refused to surrender. In the end, Mizuki would succumb to the strain placed upon him by the G4 and die. The G4's AI attempted to rise and continue the battle, but was destroyed by Hikawa.


01.Rider War


Video Game appearances

Kamen Rider Agito video game

In the Kamen Rider Agito game for the Playstation, while G3/G3-X has limited fighting time and will instantly K.O after the time is over, G4 doesn't suffer that limitation, possibly because G4 is a more advanced version and has successfully eliminated the weakness of G3/G3-X system.

Kamen Rider Battride War II


G4 in Kamen Rider Battride Wars II.

G4 reappeared in Kamen Rider: Battride War II.

Kamen Rider G4


Kamen Rider G4

Main article: Kamen Rider G4
  • Head height: 198 centimeters (6ft 4in)
  • Base weight: 150 kilograms (330.6lbs)
  • Ability perimeters
  • Punching power: 4t
  • Kicking power: 13t
  • Maximum jump height: 25m (82ft)
  • Maximum running speed: 100m/7.5s (328ft/3.5sec)
  • Vision: 15 km approx. (9.3 miles)
  • Hearing: 15 km approx. (9.3 miles)
  • Defense Rating: 8

Kamen Rider G4 was an upgraded version of the G3 system conceptualized by Sumiko Ozawa from the G3-X model. However, the G4 was deemed far too dangerous for use, so Ozawa never included the adjustments in the design schematics. But, Risako Fukami would steal the plans and construct the G4 System herself, adding a Prediction System to improve the AI and make the G4 the most powerful weapon on Earth. Unlike earlier G-Series of Kamen Riders motif based on Kuuga, G4's motif was based on Kamen Rider Agito.

Physically, G4 would reflect Agito's Burning Form, but the horns on G4's helmet resemble Agito's crest horns (unopened) from his basic Ground Form. The rest of the armor re-uses the design of the G3-X design, save for the shoulders which are held over from the original G3 design.


  • GM-01 R4 - A modified version of the Kamen Rider G3's GM-01 "Scorpion"; a modular magnum pistol, stored on right hip, hand-carried in use.
  • Gigant - A shoulder-mounted missile launcher, mounted over the right shoulder when in use. Used as a finisher.

Rider Cards

Kamen Ride G4

Kamen Ride: G4

G4 in Episode Yellow

G4 as summoned by Diend Complete Form.

Behind the scenes


Shiro Mizuki was portrayed by Ryo Karato (唐渡 亮 Karato Ryō). As Kamen Rider G4, his suit actor was Jiro Okamoto (岡元 次郎 Okamoto Jirō).

Rider notes

  • G4 can be considered the first movie-exclusive Kamen Rider of the Heisei era.
  • In terms of the users (Hikawa and Mizuki), the utilization of the G3-X and the G4 exo-suit near the end of Project G4 is reminiscent of the final battle between Kuuga Ultimate Form and N-Daguva-Zeba.
    • Shiro Mizuki and N-Daguva-Zeba also happen to be more willing to die (and end up doing so) for their motives, with Mizuki fighting for his ideals in life, and N-Daguva-Zeba fighting to accomplish either one of his goals.
  • Unlike the majority of Heisei who are based on the Primary Rider in their respective series, G4 is the first one based on the Secondary Rider.