Hmmm. While this is an interesting idea, I hope you don't mind my pointing out a few things that might have been done better.

The first thing that really hit me as a problem is the pacing. This story feels like it is moving far too fast in places. This is probably exacerbated by removing the formatting I imagine you used to break up scenes and to note the passage of time, but I think this would still be something of an issue even without that. The rate at which problems are introduced, and then solved, the rate characters are introduced at, it all just feels too rushed. Enough happens in these first two chapters that they could have been four or five chapters long by themselves. While all of the events relating to Ranma/Usagi getting settled in Nerima were going on, you could have dropped little bits of foreshadowing as to what is coming. Most, if not all of your readers know that the Dark Kingdom situation is looming on the horizon, while unknown to nearly everyone. Dropping in a few news reports on mysterious rash of deaths and/or comas that have been occurring around Tokyo with no know cause, or rumors of a masked vigilante going by the name Sailor V would have let you more gradually develop what was going on in Nerima, while still keeping it connected to what I presume to be the main plot. Showing more time passing might also have been able to mitigate my other main source for criticism, Ranma him/herself.

My problem here is that you've basically thrown Ranma out of the story. As far as I can tell, the Usagi in this story is the canon Usagi, with Ranma's martial art skills, a few of his enemies, and the neko-ken thrown in. You have Genma mention that Ranma and Usagi's personalities appear to be merging, but as far as I can tell, it is all Usagi. The spped which she 'goes girl', and rejects her original name indicates to me that there isn't really anything substantial left of Ranma in there. I'm surprised that Genma didn't spend longer trying to find some sort of cure, or at least ask if there was a Spring of Drowned Man. Given the canon existence of personality altering springs, what happened to Ranma shouldn't really take the guide by surprise (the not changing back, on the other hand). If Genma had tried to use some of the Springs to change Ranma back, and was able to succeed well enough that Ranma and Usagi would basically be timesharing the body, well, I think I would probably find it a lot more palatable than Usagi hijacking Ranma's body and skills.

Anyway, thanks for reading through all of this, and thank you for writing.

Jorlem