Fuuto PI (Japanese: 風都探偵, Hepburn: Fūto Tantei) is a Japanese manga series written by Riku Sanjo and illustrated by Masaki Sato. It is a manga sequel to the 2009 tokusatsu live-action series Kamen Rider W, part of the Kamen Rider franchise. The manga was created by Sanjo in response to the immense popularity of Kamen Rider W, serving as a sequel while exploring darker stories. It has been serialized in Shogakukan's seinen manga magazine Big Comic Spirits since August 2017, with its chapters collected in 19 tankōbon volumes as of October 2025.

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.

An anime television series adaptation by Studio Kai, Toei, and Ishimori Entertainment aired from August to October 2022. An anime film, subtitled Kamen Rider Skull no Shōzō, premiered in November 2024.

Critics praised the manga for its compelling mix of mystery and dynamic fight sequences. Similarly, the anime adaptation was lauded for effectively introducing the Kamen Rider concept to new audiences, despite being a sequel to the original television series.

Taking place two years after the Kamen Rider W TV series' finale, Fuuto PI sees the return of Shotaro Hidari, a private detective who works at Narumi Detective Agency, and his partner Raito "Philip" Sonozaki, the sole survivor of the Sonozaki family who can access the Gaia Library as research for Shotaro's work. Together they transform into the superhero Kamen Rider W, who protects the city of Fuuto from Dopants, monsters created by items called Gaia Memories. They solve cases alongside their boss, Akiko Terui, who often joins their investigations with her husband, Ryu, a member of the police force who is also the Kamen Rider Accel.

One day, Shotaro encounters an amnesiac pink-haired woman named Tokime, who is being targeted by Dopants. After saving her, they decide to hire her at Narumi Detective Agency as their assistant. As Shotaro and Philip solve more cases, they gradually uncover Tokime's connection with a man, Yukiji Bando, known as Aurora Dopant, and her past life, along with the true potential of Gaia Memories' next stage used by Dopants in their human forms, dubbed High Dopes. Philip is able to confirm that the broken Joker Memory has not been used by Tokime before explaining everything he has learned about Bando, including his involvement with a group known as Foundation X.

As Tokime asks to be told everything about Kamen Riders, Gaia Memories, and Museum to better understand her connection with Shadow Fuuto, Shotaro tells her about "Begins Night". Ever since his childhood, Shotaro idolized detective Sokichi Narumi, who protected Fuuto as Kamen Rider Skull. When Shotaro became a teenager, the detective invited Shotaro to be his new assistant. One night, Sokichi accepted a job from the mysterious Shroud to rescue Philip from the Sonozaki family as he was being manipulated to create Dopant. During the mission, Sokichi sacrificed his Skull Memory to free Philip. After convincing Philip to come with him to decide his own fate and find his own atonement, Sokichi was shot in the back by the Sonozaki family's hired men and dies, telling Shotaro to continue in his place and giving him his white fedora. Upon seeing Shotaro's grief over Sokichi's death, Philip understood his sins and decided to become the next Kamen Rider alongside Shotaro.

Among the numerous installments based on the Kamen Rider franchise television series, the Kamen Rider W 2009–2010 Japanese tokusatsu drama remained one of the most popular even a year after its release, leading to demand for new works featuring it. Producer Hideaki Tsukada approached writer Riku Sanjo to helm a manga sequel. Tsukada expressed satisfaction with Sanjo's work, noting that it successfully retained the core elements that made Kamen Rider W appealing. However, Sanjo observed that certain characters from the television series could not be incorporated into the manga. Initially, the creative team was given considerable freedom in developing the story, but Sanjo believed collaboration would yield better results. He opted to work closely with Tsukada and Toei Company to refine the narrative. The manga format also allowed Sanjo to explore storytelling without the constraints of live-action special effects. When selecting a lead artist, Toei sought someone already familiar with Kamen Rider W to ensure consistency with the series' aesthetic. Sanjo praised the inclusion of Masaki Sato as the primary illustrator, while Katsuya Herada contributed to designing the villains. Due to the publisher's stipulations, protagonists Shotaro and Philip were not permitted to resemble caricatures of their live-action actors, requiring unique character designs.