So the basic overall genre of the story is sci-fi but with a regression (basically like a time loop) twist.
It is set in the world of Alien Stage (so all canon events are included) but from the POV of a completely original character.
This OC is a member of a human rebellion working to stop the Alien Stage from continuing like it has (I should prolly go into a few more details about the plot of the original
no spoilers though
)
Basically, aliens have invaded earth. Multiple different kinds of aliens too, and earth is destroyed. Almost all of the humans are living in captivity and the rebellion is trying to save them because oftentimes they'll be used in entertainment that will result in the majority of them dying. The Alien Stage is one such entertainment (I headcanon that there are more kinds though, the world building of the original is pretty shallow). On the Alien Stage, they pit two humans at a time to sing in a competition against each other, and the loser of the competition gets killed at the end of the song. These humans were mostly all raised together in a place called "Anakt Garden" and are around 20-30 years in age.
Back to the plot of the fic though
so this OC first allows everything that happened on the Alien Stage to happen without changing anything. This results in her dying at the end of the storyline along with just about everyone else (there were like, three survivers of the Alien Stage, which is more than there would have been but still).
She doesn't die there, though. She finds herself returning to a week before the Alien Stage begins, and is given a chance to start again.
As she continues to fail and reset again, she finds that she doesn't want to save all of the humans from the stage like she wanted to at first, as some of them end up killing her or becoming obstacles in some "rounds" of her regressions.
But as time goes on, she will grow to learn more about each canon character as she manages to rescue them from the Alien Stage. Her one goal is to find whoever is forcing her into this cycle so that she can break out, but she can't get past the Alien Stage for a long time.
That's because (spoilers) she does actually have to save the humans from the Alien Stage, she just needs to learn the exact method and order how to.
When she figures out the first key, she can get to the next part of the plot. The Alien Stage (which takes over ten regressions to finally live past) is simply a small part of the overall plot.
Low-key, this just explains everything that I've already written while leaving a few key pieces out in case anyone wanted to read it
I suddenly felt the urge to stop here cos I don't want to spoil any more than this, but honestly this is just a small part of everything that happens 
Throughout the story, the OC learns more about humanity and also the aliens as she first gets dissociative and then finds herself unable to help herself from learning more. It also builds on each of the canon characters (including extremely minor ones) and the rebellion and the universe itself.
It takes heavy inspiration from Doctor Who, Red Dwarf, Ender's Game, and the Discworld, as well as Omniscient Reader's Viewpoint (it's a combination of everything I've ever loved basically, which is what all my fics are basically)
So far in my writing, I'm about 14% of the way through the storyline
and it'll take another three years to complete probably
I love it though, and I'm really happy with what I've built up 