Cinderella Boy

A goofy little oneshot by Monkey Punch from 1980.  This, plus another oneshot that retells this same story, were the inspiration for the Cinderella Boy anime that came out in 2003.  There's another oneshot that was published later, but I haven't been able to find a copy of that yet.
If you've seen the anime, I will mention that the manga has a very sad lack of my favorite character, Alamis de Panini.
If you haven't seen it, go watch it!  It's short and light. 
And Monkey Punch.
Ranma and Rella run a detective agency, but they discover a dark secret held by a big mafia and "have an accident".  They are saved from death by mysterious scientists, but not without some side-effects..