This is a really rough outline for a Ranma/Sailor Moon crossover type story. Been bouncing around in my head for over a month now and it still needs some plot points polished but I'm stuck...
Story idea...
Ranma is the twin brother to Michiru during the time before the fall, Michiru as senshi and candidate growing up, Ranma grows up to become commander of Neptunes space military and second only to his sister in terms of power. They were close growing up as royal children, and Ranma even helped cover for his sister when she first fell in love with the Uraisan princes and fellow senshi. Ranma felt the connection to Michiru break just as his fleet was destroyed fighting the to a hordes unleashed by Beyrl and Metallia, just as Michiru felt Ranmas death in the end.
Serenity don't know she had also sent others forward with her senshi and her daughters lover.
In the rebirth timeline, many times when the senshi of Neptune was near death or unable to act, the reason for Ranmas water magnet status causes many interesting issues as the planetary mana tap seeks a female member of Neptunes house to assume the mantle. But each time, Neptune is restored her power returns to her, but building a stronger connection to Ranma-chan's cursed form and causing her star seed to mature.
As Ranma battles Safron finding his skills are not quite enough to contain him, he finds the power of the senshi star seed. This time however, Ranma unwittingly create a cascade no one even the original creators of the senshi mana taps could ever expect and fully assumes the power of Neptune, while Michiru suddenly collapses after the sailor scouts defeat their latest enemy.
So now Ranma is the acting Senshi of Neptune while Michiru finds herself without her mana tap. Can Setsuna find the cause of their latest complication and sort it out before it's too late and the next enemy arrives? And how will Ranma adjust to being Neptunes senshi hier? And why does Michiru now seem to know more about military arts and Martial arts than before. And what does Usa know that she is so afraid will happen if she slips up while in the past this time?