Looking for fics where the Author has Jusenkyo curses lock when the body is put into a situation that isn't possible for the alternate form. Such as Pregnancy or Periods. Or say for Herb or Ranma something as simple as using a tampon. The space isn't there on the male body so its locked while that is in use.
Or another way of it happening is say during a period it being infinitely more painful to turn male because the parts that need to do their business aren't there in male form.
Just that kind of situation. The crossovers don't matter being close to canon doesn't matter. Just looking for these fics to see what purpose making use of this kind of lock is put to.