In 2019, a rift to another dimension suddenly opens in the skies above, revealing a "turnabout" alternate world called "Shinkoku Nippon." This parallel version of Japan maintained its militarism and remains stuck in the Showa era. Shinkoku Nippon invades our Japan with its "Genmu" gas weapons and giant humanoid "Garan" weapons. The invaders immediately take over our government and all but conquer Japan. As a result, our Japan never ushers in the Reiwa era. A decade later, our Japan has been revamped as Genkoku Nippon, a puppet state of Shinkoku Nippon. Under harsh censorship, the once thriving manga, anime, idol, and similar sub-cultures have completely died off...or so it seemed.

Shoutarou Hidari, a hard-boiled private investigator from the Narumi Detective Agency, lives for the sake of protecting the peace in the city of Fuuto alongside his inquisitive partner, Philip. One fine night, Shoutarou encounters a mysterious woman named Tokime, who is soon linked to several cases of homicide and theft. Shoutarou's investigation leads him to people using "Gaia Memories"—memory units similar to thumb drives holding vast amounts of data—to turn into formidable beasts called "Dopants." While the majority of Gaia users were put down by the detective team in the past, a number of them still remain, posing a great threat to public safety. Once more, Shoutarou and Philip, Gaia users on the side of justice, must fight as Kamen Rider W—the renowned hero safeguarding Fuuto—to eradicate the nest of villainous Dopants, all while uncovering Tokime's true identity and confronting the long-forgotten past.

In Florida, 2011, Jolyne Cujoh sits in a jail cell like her father Joutarou once did; yet this situation is not of her own choice. Framed for a crime she didn’t commit, and manipulated into serving a longer sentence, Jolyne is ready to resign to a dire fate as a prisoner of Green Dolphin Street Jail. Though all hope seems lost, a gift from Joutarou ends up awakening her latent abilities, manifesting into her Stand, Stone Free. Now armed with the power to change her fate, Jolyne sets out to find an escape from the stone ocean that holds her. However, she soon discovers that her incarceration is merely a small part of a grand plot: one that not only takes aim at her family, but has additional far-reaching consequences. What's more, the mastermind is lurking within the very same prison, and is under the protection of a lineup of menacing Stand users. Finding unlikely allies to help her cause, Jolyne sets course to stop their plot, clear her name, and take back her life. [Written by MAL Rewrite]

Second part of JoJo no Kimyou na Bouken Part 6: Stone Ocean.