I'm not sure. It depends on how the story is presented and the background information provided. Sometimes, stories labeled as such can have elements of truth mixed with fiction.
A 'rewind novel' could potentially be about a number of things. It might be centered around a character who has the ability to rewind time, either physically or through some sort of mental power. The story could then follow their adventures as they use this power to change the course of events. Or perhaps it's a more metaphorical 'rewind', where the narrative jumps back and forth in time to tell a complex story, revealing different aspects of the characters and their relationships at different points in time.
The official Fortnite is mainly focused on battle royale, building, and fun adventures. It has a broad audience including kids and teenagers, so it would never have something like an 'erotic story'.
The movie 'Rewind' is not a true story. It's likely a product of the imagination of the filmmakers, crafted to engage and captivate the audience with an interesting plot and characters.
It's hard to say for sure. While Fortnite is known for its elaborate and ever - changing events and story arcs, the 'black rain fortnite story' might or might not be official. If it is official, it would likely be promoted within the game, through announcements and in - game cues. However, if it's not, it could be a grassroots idea from the Fortnite community that has spread around. Some unofficial story ideas do gain traction and sometimes even influence the developers to consider incorporating similar elements in future official content.