Alright, as far as workshopping an actual plot premise, bit of a long one, but...:

[hider=Where We Came From]
[i]In the twilight hours of a forgotten time and place, a mad priest waged the final stage of a generational grudge match, seeking [Heaven] and to put an end to the family of heroes that had opposed his tyrannical self-styled god that he called his friend. Yet... if would be in the reliance on that bond with his friend that foiled him. The last "Son of God", drawn by the call of their blood as surely as any of his brothers, finally arrived upon the cusp of victory. And as the priest reached [Heaven], the son chose to deem him unworthy. In the end, the son could not truly undo what [Heaven] had done, what the priest had started, but he still foiled the priest's attempts to dispose of the heroic rivals of his friend. The disturbed course of [Heaven] resolved, and the world was irrevocably altered.[/i]

In essence, Giorno was implied to have been in Florida during Stone Ocean but didn't arrive in time. In this AU, he arrived near to the final battle, shortly after Pucci attains [C-Moon], and though I'm using Eyes of Heaven to say Requiem wasn't enough to nullify or revert the Time Acceleration/power of Heaven with Return to Zero, [Gold Experience Requiem] still had the raw physical stats to oppose even [Made in Heaven's] insane speed, and its healing prowess kept nothing from truly sticking. The result is that no-one from the gang died except Foo Fighters and Weather. Similarly, just as when Emporio defeated Pucci canonically, killing him doesn't stop Time Acceleration from operating; it just stops it from reaching Pucci's desired result and resets the universe one last time... except things come out "wrong" and different.

This altered course leads to the universe resetting as something that could theoretically be called an "alternate Part 7", except very much not. The characters of Part 7 do not exist; there's no Johnny or Valentine, for example. In exchange, somewhere out there, the Joestar family has survived and -in a sense- finally truly ended to eternal grudge match with DIO once and for all with the act of his last son making peace with them. Though, while the Joestar and Brando no longer bear any destined fate to clash, those that bear the star-shaped birthmark upon the back of their shoulder still find themselves generationally drawn into bizarre troubles time and time again.
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[hider=Where We Are]
The year is now 2020, over a hundred years since the universe was reset to the late 1800's. While the people have changed, the course of history and the nations and events that formed from it have largely gone unchanged simply due to being fated to occur, regardless of the reset. Entire generations have come and gone, and those that remember the madness caused by the bizarre event that altered the very course of history are long gone. The Universe Reset and the immediate aftermath looms in the distant past as a mysterious source of terror for the supernatural community; for it was not merely those directly involved with contesting it that remember it. Of course, the universe reset ending early largely erased the existence of many people, because they were simply not allowed to be reborn to begin with, but those like Stand Users remembered and survived, thrust into an unfamiliar time and place and forced to rebuild their lives, even with history retroactively altered to support their continued existence. Those born after them in the century leading up to the present sometimes have some vague subconscious recollection of the Universe Reset, but the existence of that event has largely been consigned to myth and legend, given the lack of tangible proof remaining to support it.

Beyond that, elements of both eras have merged into coexistence. The Stand Arrows were still created from the remains of an uncovered asteroid, but they were created in even greater numbers. And furthermore, the material of the asteroid was used to create even more artifacts than them, other weapons and devices that all possess some capacity to "test" people and judge their [i]Worthiness[/i]. Hamon and the Spin have both developed independently and are -in some ways- considered rival sects of the supernatural; between them, the Spin is considered the "younger" and more "modern" art with its reliance on Steel Balls that can rarely be made practically without special equipment, along with a greater understanding of physics. The Stone Masks and the Pillar Men are no longer a thing of the past, as the twisted history has led to the resurgence of their existence; they have naturally held a long-running rivalry with Hamon users, and both have made attempts to exterminate the other whenever the opportunity arises. And all the while, somewhere out there... the Holy Corpse Parts lurk, just waiting to be assembled to grant unlimited power.

Stands are far more prevalent than they once were; as nearly all Stand Users survived the Universe Reset, there has been an entire century for their genetics containing the potential to be a Stand User to further spread out in the world. Despite this, due to their lack of physicality, Stands have managed (if only barely) to remain unknown to the wider public consciousness. The utter inability to detect or study them scientifically has sharply limited any attempts to prove their existence, even by those that do notice. This has, however, led to the growing existence of secret mundane organization (both legal or otherwise), dedicated to uncovering the supernatural and bringing it to task; some of these organizations have even lucked out and acquired the backing (willingly or otherwise) of Stand Users or other supernatural inhabitants. In the modern digital age of cameras and various high-quality records, it is growing increasingly difficult for Stand Users to conceal their bizarre nature and get away with their "shenanigans"-benign or otherwise- without consequences.
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[hider=Where We’re Going]
With all that said, to reiterate: it is the year 2020. The modern digital age is in full swing, and all the countries we know and love (or otherwise) have finished redeveloping according to Fate's design, regardless of the Universe Reset. While the [i]exact[/i] location is still somewhat undecided, the lean is towards a seaside locale in an original city named Stoneridge, located in the north-eastern USA. On the surface, this city is fairly unremarkable, but to those that live there, it is known to be a hub of gangs and social unrest teeming under the surface. The criminal elements have greatly corrupted much of the city's legal infrastructure, even to the point of influencing elections. Gangs and criminal empires constantly jocky for influence, whether it be martial, material, legal... or even supernatural, and several are known by those more in touch with the supernatural to have multiple Stand Users or other wielders of the occult in their pockets.

Recently, the wealthy owner of a large property passed away under mysterious circumstances, and with the lack of any proper inheritor for his possessions, they were "repossessed" by the city. Among those possessions, the owner was discovered to be an avid collector of what seemed to be many exotic and expensively old art pieces... amongst which was found a certain golden arrow. An appraiser identified the value of the object as having significance worth historically preserving, and the item was donated to a local museum as part of several new exhibits. And during the advertisement campaign for those exhibits... several interested parties recognized the Arrow for what it was.

It's into this brewing mess that your characters arrive, largely unaware of what is to come. For one reason or another, they are on a trip to the museum. Perhaps they're out for a day with a relative. Maybe they're on a school trip. Or maybe they're a Stand User with designs on one of the exhibits. Whatever their reasoning, they're about to be drawn into a much larger conflict over an asset that could either liberate the city from the darkness choking it... or plunge it irrevocably further into its grasp.
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