In the world of Kamen Rider Gaim, because of a large company known as the Yggdrasill Corporation setting up shop in the once bustling city of Zawame (沢芽市, Zawame-shi), it now feels like everyone is living in a jōkamachi (城下町, 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 Inves 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.

Kamen Rider Gaim (仮面ライダー鎧武（ガイム）, Kamen Raidā Gaimu) is a Japanese tokusatsu drama in the Kamen Rider Series, the 15th series during its Heisei run and 24th overall. The series, written by Gen Urobuchi, directed by Ryuta Tasaki and produced by Naomi Takebe, began airing on TV Asahi from October 6, 2013, replacing Kamen Rider Wizard in its initial timeslot and joining Zyuden Sentai Kyoryuger in the Super Hero Time programming block. The core themes of the series are fruits, locks, and the Sengoku period, and its slogan is "Rider Warring States Period" (ライダー戦国時代, Raidā Sengoku Jidai). The title character made a first appearance Kamen Rider Wizard's special episodes.