Gridman Sigma was the proposed ally of Gridman in a sequel series that was never completed or even aired. Sigma would have become the alter ego of Takeshi Todo, a reformed antagonist of the original series. Sigma would have fought a relative of Khan Digifier.
In 2015, Gridman Sigma made his first public appearance in the anime short, Denkou Choujin Gridman: boys invent great hero where he is finally partnered with Takeshi Todo.
