I wrote a fic (that I never showed anyone) that was sort of like
that.  The basic plot was:

   Saotome Ranma was walking along one day and ends up getting splashed
and changing in broad daylight.  She nervously looked around to see if
anyone had noticed and immediately spotted a woman staring at her as
though she had just sprouted a second head.  Ranma walks up to the woman
and asks her what she saw, after the woman says she saw him change sex
Ranma realizes it could mean troube if he can't convice her to remain
silent.
   Ranma takes the woman out for coffee trying to bribe her but the
woman figures out Ranma's plan and threatens to publicly reveal this
'oddity' if she doesn't get his entire story.  Reluctantly, Ranma
relents.  They return to the woman's home and he begins to tell her
everything.

<Skip entire "Ranma1/2" series>

   Ranma, feeling defeated, gets up to leave after finishing his story.
As an afterthought he ask the name of the person to whom he has just
recounted hi entire life.
   "My name is Takahashi Rumiko.  It was nice meeting you Ranma, I hope
we meet again.  I have a feeling that someday I'll owe you a lot,"
replied the woman with a freindly smile.
   Ranma returned the smile then quietly reurned to his life.

  Well, that is basically how my fic went.  Howeverthe actual fic was
much mre elaboate.  I never showed that to anyone thinking it would earn
nothing but comments of how lame my ideas can be at times.  If anyone is
interested though, I may be able to dig it up and send them a copy.
  Well, until next time, ja ne.

Sincerely,
Andrew Hubbard
Akihiro@webtv.net