Shoutarou Hidari, a tough private investigator employed by the Narumi Detective Agency, is devoted to preserving the peace of Fuuto city alongside his curious partner Phillip. One night, Shoutarou encounters an enigmatic woman named Tokime who is linked to several cases of murder and theft. Shoutarou's investigation leads him to those who use "Gaia Memories" - memory units similar to thumb drives containing vast amounts of data - to transform into fierce beasts known as "Dopants." Although the detective team eliminated the majority of Gaia users in the past, there are still some who pose a significant threat to public safety. As Kamen Rider W, Shoutarou and Philip, Gaia users devoted to justice, must once again fight to eliminate the den of evil Dopants, while also discovering Tokime's true identity and confronting a forgotten past.