In the world of Kamen Rider Gaim, because of a large company known as the Yggdrasil Corporation setting up shop in the once bustling city of Zawame, it now feels like everyone is living in a jōkamachi (castle town). To escape this feeling, young people throughout the city have formed dance crews to bring joy back into their lives. Also popular is a game that uses Lockseeds that contain small animals known as Invase that are said to come from another dimension. However, as this game becomes more and more popular, it seems to be causing tears in reality to an actual alternate dimension from which monsters are invading the Earth. Kota Kazuraba, who gives up time in his dance crew to start a job to help out his sister, uses a special Lockseed in his Sengoku Driver belt to transform into Kamen Rider Gaim to battle these monsters, but he must also contend with other rival Kamen Riders, transforming a fight against monsters from another dimension into a Kamen Rider warring states period.