Kamen Rider Agito is the eleventh installment of the Kamen Rider family of tokusatsu shows and is the first to show more than 2 riders side by side. By doing this, it established a standard for the next Kamen Rider shows, which would always include several riders on the same screen.
2 years ago, after the end of the battle between Kamen Rider Kuga and the Unidentified Lifeforms, the Japanese police build an armor called G3 Unit, wear by the officer Hikawa Makoto, to fight those enemies. However, other unknown lifeforms appears, killing non-random people in a supernatural way and, to fight them, Tsugami Shoichi, a man who lost all his memories, and Ashihara Ryo, an ex-swimmer, somehow transforms, respectively, into Agito and Gills. However, the police, Agito and Gills don't see each other as allies in this battle.