Hmm, this might work. Even allying with a troll would be worth it to defeat Saotome once and for all. "Do you know how to defeat the evil magic he has used to enslave the pig-tailed girl?"
The troll blinks and stares at you for a moment. "You really don't know, do you?"
"Know what?" Is there some secret of Saotome's that the troll has uncovered with its magic?
The troll smirks. "Yes, the rumors are indeed true. Well, I suggest dousing Son-in-law with cold water. That should banish him back to the netherworld." The troll seems to be convulsing for some strange reason.
You nod. Saotome does seem to avoid water for some reason. Now you understand why. You've seen the Wizard of Oz. That witch didn't like water, either.
"All you have to do is invite him and Akane over to dinner, and put this in his food." She waves a salt shaker. "It will make him forget all about Akane, leaving her free for you, and Ranma free to marry Shampoo."
You nod. Then a thought hits you like a brick. "What if the wrong person eats the food?"
The troll blinks. It quietly says, "Hmm... not quite that stupid." The troll then raises its voice and says, "Just don't eat it yourself. It only affects men, not women. The effects are permanent without the antidote." She pauses, and hands you a pepper shaker. "This is some of the antidote. Season your food with it and you will be immune. And don't forget which is which!"
One more thought nags at you. "What if Akane eats it?"
The troll waggles its staff at you. "She is female and thus immune."
You stand up and bow to the troll. "Excellent. I shall make preparations at once."
The troll nods. "Have a nice meal."
Heading out of the Nekohanten, you pass a street vendor selling flowers.