Kamen Rider W was the 2009-2010 entry in the Kamen Rider franchise. It was the eleventh series in the Heisei period run of the Kamen Rider Series. It premiered following the finale of Kamen Rider Decade on September 6th 2009 and ran for 49 episodes. The series is described as the “Heisei Kamen Rider 10th Anniversary Project: Fall Campaign.”
In the first episode of Kamen Rider Fourze, W is revealed to be canon to the original Showa timeline, making it the first series to do so since Kamen Rider Agito. The catchphrases for the series are “We are the two-in-one Kamen Rider” and “This clinches it!”
Many people live in peace and harmony in the fictional city of Futo, an ecologically-minded and wind-powered city. However, the Sonozaki Family sell mysterious devices resembling USB flash drives called Gaia Memories to criminals and other interested parties, who use them to become monsters called Dopants, committing crimes with the police force powerless to stop them. To make matters worse, the Gaia Memories carry a dangerous toxin that cause their users to go insane to the point where they could die from using the devices unrestrained. After the death of his boss, the self-proclaimed hardboiled (actually half-boiled) detective Shotaro Hidari works with the mysterious Philip, who possesses the true Gaia Memory, to investigate crimes which involve Dopants. Using their own Gaia Memories, Shotaro and Philip use the Double Driver belts to transform and combine into Kamen Rider Double to fight the Dopant menace and keep Futo safe. While joined in their fight by investigator Ryu Terui, who transforms into Kamen Rider Accel, the mystery of Philip’s past, his relation to the Sonozaki Family, and their Museum organization are revealed.