A detective, proclaiming himself to be hard-boiled, and a mysterious boy who is connected to “Memory of the Earth” together transform into the 2-in-1 Kamen Rider, W. They protect their city Fuuto from crimes caused by superpower-granting devices known as “Gaia Memories”.
Akiko Narumi arrives in Futo to be the landlord of the "hard-boiled" detective Shotaro Hidari, who finds himself involved in a case involving a former female love and a Dopant on the attack.
After his missing target is killed by another Dopant, Shotaro works with his partner Philip to figure out the truth regarding the killer while being dogged by Akiko and her strange sightings.
As several of Double’s Gaia Memories are taken by the Cockroach Dopant, Shotaro tries to find his true identity while Philip tries to reunite the dance partners for their legendary move.
When the search for the Virus Dopant takes an unexpected turn, Shotaro and Philip must work to find the true controller and the reason behind their grudge.
Discovering a horrible secret from Saeko and seeing his partners captured by Arms Dopant, Philip must figure a way to save them even if using the unstable Fang Memory.
As Shotaro and Philip discover the truth regarding the teens using the Bird Memory, Kirihiko discovers the truth behind Museum and his usage by the Sonozaki family.
As Ryu’s intensity and Kamen Rider Accel powers threaten to harm innocents, Shotaro and Philip must discover the reason behind his anger while putting a stop to the ice-powered Dopant.
As Horinouchi is taken by the bizarre Dr. Isaka for further usage, Akiko tries to decipher the meaning of the doll and the truth behind Horinouchi’s daughter.
A ditzy female magician who turns invisible asks Shotaro to find the seller of her Gaia Memory, which ultimately leads Terui to the man who killed his family.
Akiko and Philip desperately try to stop Terui from taking immediate revenge on Shinkuro when he becomes key to saving Lily from her deadly Gaia Memory.
As Philip is taken by the Xtreme Memory to meet with Shroud, Shotaro continues to try and figure a way to discover the culprit behind Nightmare Dopant’s attacks.
While under pressure of being abandoned by Philip as his Double partner for not keeping up, Shotaro tries to decipher the truth behind Bitou’s framing.
As Shotaro is asked to pursue a young teacher by her students, Terui also goes after her due to a remarkable similarity between her and his deceased sister.
As Akiko desperately tries to complete Tooru’s movie, the insular director is targeted by Wakana to allow her access to the full potential of her Dopant power.
Shotaro and Terui are asked by a mother to save her daughter, who has been turned old to satisfy a grudge hit as Shroud approaches Phillip and Terui, wanting them to become Kamen Rider Double Cyclone Accel Xtreme.
Terui tries to decipher the truth regarding Shroud and her intentions as she tries to force him and Philip to join together into the ultimate Double to defeat Ryubee. Meanwhile, an agent of Foundation X takes possession of the new Gaia Memories…
With Shotaro gripped by fear and Terui injured, Philip is at the mercy of his father Ryuube, who prepares to use his son and Wakana to bring about Gaia Impact.
Shotaro and Philip must endure the ultimate hardships to stop Kazu from completing his own Gaia Impact in order to complete what could be their final case together.
One year after Philip’s departure, Shotaro continues onward alone, but a case involving saving a boy’s sister from Dopant bullies brings forth a change for the better.
