Denkou Choujin Gridman: boys invent great hero (電光超人グリッドマン boys invent great hero Denkō Chōjin Guriddoman Boizu Inbento Gurēto Hīrō Lightning Superman Gridman: boys invent great hero) is a 2015 animated short film directed by Akira Amemiya and produced by Studio Trigger for the Japan Animator Expo.
It tells the story of Takeshi Todo, formerly the antagonist of Denkou Choujin Gridman, who becomes an ally of Gridman to fight evil.
Twenety-two years have passed since Khan Digifer's downfall, and Takeshi Todo, now an adult, enters a dump area filled with computer monitors. Finding a computer monitor that greatly resembles Naoto's Junk, he sees a series of flashbacks about the fight between Gridman and monsters he created with Khan's help in Computer World which culminated in the duel between Gridman and Khan Digifer himself. As he watches the flashbacks, mirages of his past monsters appear and terrorize the city. Once the flashbacks end, multiple lights from computer monitors suddenly radiate him, granting him an Accepter. The short film ends when Takeshi transforms into Gridman Sigma.