This article is about a/an machine and a villain in Kamen Rider Drive.

"I am Sigma. Ignition complete."
―Sigma Circular upon activation[src]

" defend... execute plan.... I am...Sig-"
―Sigma Circular upon destruction[src]

The Sigma Circular (シグマサーキュラー Shiguma Sākyurā), referring to itself as Sigma (シグマ Shiguma), was a sentient machine that Gold Drive and Roidmude 004 created in order to dominate all of humanity.


During the first attempt to activate this machine, Medic was originally meant to be a sacrificial vessel, but Brain takes her place to save her from brainwashing and sacrifices himself instead. Who Loves Heart the Most?

After his escaping, Gold Drive and the Reaper Legion infiltrated the Special Defense Center headquarters, and placed Sigma under evolution process before the Kamen Riders (and later joined by the now-defected Roidmude generals Heart and Medic) would stop him from his plan on occurring the second Global Freeze. What is a Roidmude's Last Dream?

Sigma Circular destroyed

Sigma Circular destroyed by Drive and Heart Roidmude

Sigma's evolution was completed and activates the second Global Freeze just before Drive and Heart arrived to stop the machine. Sigma was destroyed by the combining finisher attacks of Drive Type Tridoron's Rider Kick and Heart Over Evolved's strength punch. With its destruction, the Global Freeze ends and all humans who were transformed into data were returned to normal. Why Must They Fight? Who Will You Entrust the Future to, My Friend?


Sigma Circular (Sphere)
KRDr-Sigma Circular sphere

Sigma Circular (Sphere)

  • Appearances: Drive Episodes 44-45

Sigma Circular
KRDr-Sigma Circular

Sigma Circular (Mecha)

  • Height: 234 cm
  • Weight: 242 kg
Heavy Acceleration
As with all Roidmudes, Sigma Circular is capable of slowing down the movement of surrounding objects, including that of humans, with their unaffected consciousness aware of their impass during this time. One can be protected by the Heavy Acceleration effect by carrying Shift Cars or Signal Bikes on their person.
Global Freeze
Having absorbed the energies of all four Promised Numbers, Sigma Circular can generate a second Global Freeze. However, this time, not only it decelerate one's movements to the point where they are completely unable to move, it also digitizes humans into data and thus creating a new world under Banno's will. Even those who possess regular Shift Cars and Signal Bikes are also affected. Only Roidmudes who have achieved Over Evolved and Drive in Type Tridoron are shown to be able to move freely, however Medic was an exception, possibly due to Banno's reprogramming on her. While advanced Shift Cars like Shift Formula and Shift Deadheat, which are able to resist Super Heavy Acceleration, allow users to move freely as well, these users are still affected by the digitization process.
Barrier Generation
Sigma can generate barriers as means of protection. However, the barrier it created must be plugged into a circuit which vulnerably can be deactivated.
Stalagmite Generation
Sigma can unleash teeth-like stalagmites for defense. It can also channel this power in a wider range.
Despite not having legs and limbs, the machine still capable of moving around by levitation.
Physic Explosion
Sigma can create physic waves that explodes on contact.
Laser Beam
From its head, Sigma can release a small energy beam for offence.
Sigma can move itself at a very high speed so much that it seems as it teleported.
Energy Wave
In a similar vein to the Promised Numbers, Sigma can launch a powerful purple shockwave.
Energy Shield
Sigma can create hexagonal shields for defense, able to resist the attack of Tridrop.
An ability inherited by Banno, Sigma can generate red digital tentacles that capable of constricting its foes.
  • Appearances: Drive Episodes 46-47

Behind the Scenes


Sigma Circular was co-voiced by Ayumi Fujimura (藤村 歩 Fujimura Ayumi), and Masakazu Morita (who also portrays Tenjuro Banno).


Sigma Circular Giant Teeth

Sigma attacking Tridoron

  • If the word "Sigma" were changed to the Greek letter ∑, its name ∑-Circular would resemble that of Mashin Chaser's E-Circular weapon.
  • The giant teeth-like structures generated by the Sigma Circular have been seen in the show's opening since the very first episode.



Icon-drive Kamen Rider Drive
Kamen Riders
TV Series: Shinnosuke Tomari - Go Shijima - Chase - Tenjuro Banno - Kamen Rider Mach (Production Model) (Jun Honganji)
Movie/Special/Stageshow-exclusive: Zoruku Tojo - Kyoichiro Kuroi - Kamen Rider 4 - Paradox Roidmude - Heart - Brain
Special Investigation Unit
Shinnosuke Tomari - Kiriko Shijima - Krim Steinbelt - Jun Honganji - Genpachiro Otta - Rinna Sawagami - Kyu Saijo

Unofficial Members: Roidmude 072 - Go Shijima - Chase - Mitsuhide Nira (defected)

Other allies
Akira Hayase - Harley Hendrickson - Kyoichiro Kuroi - Eisuke Tomari - Eiji Tomari - Ninningers - Ryu Terui - Takumi Inui - Yuto Sakurai - Sakuya Tachibana - Kamen Rider Blade - Kamen Rider Chalice - Kamen Rider Leangle
Creator: Tenjuro Banno

Generals: Heart - Brain - Chase (defected) - Medic - Freeze - Krim Steinbelt (copy) - Roidmude 005 - Roidmude 006 - Tornado - Paradox

Minor Advanced Roidmudes: Reaper Legion - Iron Roidmude - Paint Roidmude - Crush Roidmude - Scooper Roidmude - Volt Roidmude - Gunman Roidmude - Voice Roidmude - Judge Roidmude - Shoot Roidmude - Shocker Buruburu - Angel Roidmude

Fusion Evolution State: Sword Roidmude - Seeker Roidmude - Open Roidmude - Cook Roidmude - Thief Roidmude

Unofficial: Mitsuhide Nira - Sigma Circular

Other villains
Zoruku Tojo - Imitation Drive - Kibaoni Army Corps - Shocker - Neo Shade - Ganma (Da Vinci Gamma)
Mu:Leader of Mu
Executive :Shocker Leader III
Kamen Riders :Kamen Rider Dark Kiva - Kamen Rider Poseidon - Kamen Rider Wiseman - Kamen Rider Duke - Kamen Rider Dark Ghost - Kamen Rider Another Para-DX
Monsters :Cancer Zodiarts - Gremlin - Demushu - Gamma Superior - Graphite
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