Takeshi Hongo is a promising young man with a passion for motorcycle racing. However, his dreams are suddenly ruined when he gets kidnapped by Shocker, the evil secret organization planning to dominate the world. After being remodeled into a cyborg, Takeshi escapes and swears to protect the world from the inhuman monsters.

A lawyer with a big personality works with an straightlaced recent law graduate on various law cases in Japan.

An amnesiac, happy go lucky youth named Shoichi Tsugami uses the power of Agito to unravel his mysterious past and battle beings known as Unknowns. In response to the Unknown threat, the police unleashed their newest weapon, the G3 powersuit primarily used by Makoto Hikawa. More mysteries unfold with the appearance of Ryo Ashihara, who transforms into a pre-Agito known as Gills. He seeks the truth about his father's suicide. These mysteries and others collide, as the true nature of Agito would ultimately determine the fate of humanity.

High school student Shun Takahata is bored. Bored with the day-to-day monotony of school and life, he prays for change, for something exciting. Suddenly, he and his classmates are forced to play deadly children's games and facing terrifying creatures from a talking Daruma doll to a sharp-clawed lucky cat.

The DarkZide stealthily appeared on Earth from their dying world in Dark Dimension to acquire the Larmu, human life-energy, to continue their existence. To counter the threat, Takeshi Munakata of the Cabinet Secret Service established the group S.A.I.D.O.C to intercept the DarkZide. S.A.I.D.O.C developed the Crystal Power needed to completed the Changérion project. However, the power was accidentally transferred into the body of detective Akira Suzumura.

Shouichi encounters a teenage girl called Sayaka, who ran away from a military facility because of an attack by the Ant Lords. Sayaka has a supernatural ability to foresee the future. Risa Fukami, of the military group GA, wants to use that power to enhance the newly-made G4 System, which was based upon designs stolen from Ozawa. Now, Agito and Gills must fight to stop the Ant Lords' attack, as G3 and G4 settle their score.

Attorneys Kensuke Komikado and Machiko Mayuzumi receive a request from a general hospital. They go up against veteran attorney Kazuma Kujou who is trying to extract money from the general hospital by a medical malpractice lawsuit.