|Human Host/Form:||Takeshi Todo|
|Height:||Micro ~ 70 m|
|Weight:||0 ~ 56,000 t|
|Place of Origin:||Hyper World|
|Transformation Item:||Gran Acceptor|
|First Appearance:||Denkou Choujin Gridman: The Demon King's Counterattack|
|Last Appearance:||Denkou Choujin Gridman: boys invent great hero|
|Affiliation:||Gridman (older brother)|
Gridman Sigma (グリッドマンシグマ Guriddoman Shiguma) is the younger brother of Gridman in a novel sequel series, Denkou Choujin Gridman: The Demon King's Counterattack. Sigma would have become the alter ego of Takeshi Todo, a reformed antagonist of the original series.
In 2015, Gridman Sigma made his first public appearance at the end of the anime short, Denkou Choujin Gridman: boys invent great hero.
Girdman Sigma was created both for the serial novel and Kazumitsu Akamatsu's desire to have both Thunder and King Gridman to fight side-by-side, hence his later form as King Gridman Sigma.
This plan was formulated back during the production of the original show. In the third quarter of the series, Takeshi Todo was meant to steal Gridman's data and become Khan Knight (カーンナイト Kān Naito), a rival character and Khan Digifier's servant, before redeeming himself as Grid Knight (グリッドナイト Guriddo Naito). Additionally, had the original plan taken place without the aforementioned production problems, Grid Knight would star in a sequel season. As revealed in an old magazine called Denkou Choujin Gridman 2: Great Determination! Great Monster Encyclopedia (電光超人 グリッドマン2 たいけつ!かいじゅうだいずかん Denkō Chōjin Guriddoman Ni Taiketsu! Kaijū Daizukan), there was a design of a second Gridman, who was themed after a European knight. Despite his near-identical appearance to Gridman save his head, Sigma is designed by anime Mecha designer Hideo Okamoto (岡本 英郎 Okamoto Hideo).
- First picture: Grid Knight - The white armor parts are inherited from Gridman and are meant to represent silver/metal.
- Second picture: Khan Knight - Aside from its black colored body, Khan Knight's undersuit is identical to Grid Knight's, having black and purple colors.
- Third to fifth pictures: Gridman II, the designs of a new Gridman, who bears resemblance to a knight.
Denkou Choujin Gridman: The Demon King's Counterattack
When Neo Khan Digifer, the younger brother of Khan Digifier attacks, Gridman and his own younger brother, Gridman Sigma appears. Choosing Takeshi Todo as his host, Sigma and his brother fight Neo Khan Digifer and his monster army. Their final opponent was Geist Digifer, which was Neo Khan Digifer's final form achieved by fusing with the souls of his defeated monsters.
Denkou Choujin Gridman: boys invent great hero
Takeshi appeared as an adult in the anime Gridman short. After watching the battles (or rather, relieving past memories) of the previous Gridman, Takeshi is granted the Acceptor by the light of several monitors and transforms by shouting 'ACCESS FLASH'. Transforming into Gridman Sigma to face monsters in the real world
- Height: Micro ~ 70 m
- Weight: 0 ~ 55,000 t
- Flight Speed: Mach 30
- Origin: Hyper World
- Gran Acceptor (グラン=アクセプター Guran Akuseputā): A bracer on Gridman Sigma's right arm, it is connected to the Acceptor worn by Takeshi.
- Grid Sigma Beam (グリッドシグマビーム Guriddo Shiguma Bīmu): Gridman Sigma's version of the original Grid Beam.
- Sigma Slash (シグマスラッシュ Shiguma Surasshu): Gridman Sigma conjures a blade of light to slash with.
- Combine: Like Gridman, Gridman Sigma can combine with Dyna Dragon to become King Gridman Sigma. This also implies that he can use the other Assist Weapons as well.
- Double Grid Beam (ダブルグリッドビーム Daburu Guriddo Bīmu): Gridman and Gridman Sigma fire their signature finisher beams simultaneously.
- Lightning Rotation Slash (電光回転切り Denkō Kaiten Giri): Gridman and Gridman Sigma both slash the opponent.
King Gridman Sigma (キンググリッドマンシグマ Kingu Guriddoman Shiguma) is the fusion of Gridman Sigma and King Jet, the latter acting as its armor.
- Powers of King Gridman: The actual details are unknown, but it is presumed that he retains the same powers and armaments as King Gridman.
- Main article: Category:Assist Weapons
In the same vein as Gridman, Sigma can also arm himself with Assist Weapons (アシストウェポン Ashisuto Uepon), specifically ones that his brother uses. Given that Khan Digifier had destroyed them in his final battle, it is more likely that they were recreated/repaired at some point of time.
- King Jet (キングジェット Kingu Jetto): A large aircraft made to be Dyna Fighter's support. Sigma combines with it to become King Gridman Sigma.
Denkou Choujin Gridman: boys invent great hero
- Masaya Obi, the actor of Naoto Sho has Gridman Sigma's version of Acceptor. Whether it was the original prop or his own custom made is unknown.
- Sigma's blue design would be later used in many other Ultras.
- His face resembles the faces of Jean-Bot and Jean-Nine.
||Mirrorman | Falcon | Redman | Red Fighter | Green Fighter | Orange Fighter | Triple Fighter | Jumborg Ace | Jumborg 9 | Fireman | Izenbo | Koseidon|
||Gridman/Servo | WoO | Mirrorman Reflex | Gridman Sigma | Don Shine|
||God Zenon | Dyna Dragon | Mountain Gulliver No. 5 | Reimon | Mirror Knight | Glen Fire | Jean-Bot | Jean-Nine | War God | Powered Zenon | Gridknight|