In the city of Fuuto, criminals make use of USB-like devices called Gaia Memories to turn themselves into superpowered monsters known as Dopants, wreaking havoc in the otherwise peaceful city. However, there are also heroes who utilize the Gaia Memories to fight these criminals, one of whom is the self-proclaimed, hard-boiled detective Shoutarou Hidari. With the help of his witty partner Philip, the two transform into Kamen Rider W—the legendary hero of Fuuto city.