That can be a problem though... and not even limited to Ranma fandom... Too often I see writers whom what to 'tell their story', the problem is getting to thier stry from canon material... many times I've seen the whole backdrop of events left out and the reader never is to learn how the protagonist got to that point.
An obvious Ranma example of the stories I'm talking about are ones that start with Ranma having left Nerima and is on his own, and in some cases it is much later that the story starts (remember one that started a whole 3 1/2 months after he left)... Why leave out the reasons and all that time? Because generally I find the author wants to tell *their* story, and did not so much care to bother telling how it came to that point, but only that they could start telling it.
To me, setup and backdrop is important... I prefer reading as much of it as possible, as I like to immerse myslf into the story. If the setting, setup, and backdrop ar not believable, I am likely to not like it near as much.
It can get very troublesome either way. Leaving out the "how things got here" can be much better sometimes, while other times it sucks BAD.
Then you can do it as i am doing now, write the "backdrop" as a story of its own. In my case, that backdrop is already past 100k words posted, and since it spans 5-6 years it´s way slower paced than i wanted.
OTOH, trying to jump right into the main part of the story without it, in this case that would probably just make most readers go "eh?"... And again OTOH, it´s got about 400+ readers for all chapters, so clearly there´s plenty of people that enjoys a story doing "just" the backdrop as well.
Essentially, you have to decide on how to do it, and it´s almost guaranteed that it will never be perfect.
When I do AU (about half of them) i do what i can to explain the situation and make things make sense.
But I won't describe the Tendo home, or the scenery, or what they are wearing past minimal things.
...
That's it for describing that. No needless detail or anything. And I don't describe body parts past basic size. IE, She was 4 foot 11. And I try not to go crazy with hair color. Purple hair, redhead, blue, not NAVY, not lavender, just the colors.
Yeah, that´s similar to what i prefer as well. Seen too many stories, including faar too many professionally published books spending pages and pages on "watching the scenery", making them slow and even boring to read.