The series follows Shotaro Hidari, a private detective at the Narumi Detective Agency, and his partner, Raito "Philip" Sonozaki. Together, they solve cases and combine their abilities to transform into the superhero Kamen Rider W, defending Fuuto City from threats alongside new allies. Set two years after Kamen Rider W, the manga shifts focus more toward Shotaro rather than Philip. This led to the introduction of Tokime, an amnesiac woman who becomes Shotaro's assistant and is mysteriously connected to the new enemies they face. Since the manga was published in a seinen manga magazine, Sanjo incorporated more mature themes—content that would not have been possible in Kamen Rider W.
