Shoutarou Hidari, a private investigator from the Narumi Detective Agency, partners with Philip to maintain peace in Fuuto. Their investigation into a series of homicides and thefts involves a woman named Tokime, whose involvement is linked to these crimes. As they delve deeper, they uncover that Gaia Memories – small units storing vast data – are used by some individuals to transform into powerful Dopants.
Shoutarou and Philip, who possess Gaia Memories and use them for justice, fight as Kamen Rider W to eliminate the Dopant threat and uncover Tokime's true identity, all while confronting unresolved aspects of their past.