Manga: Ranma Saotome has just gotten back the legendary Cursed Springs (Jusenkyo) of China and has been engaged by his father and his best friend, Genma and Soun, to Akane Tendo, Soun's daughter. Ranma and Akane are off to a rough start and it doesn't help that Ranma has a curse from Jusenkyo: turning into a girl when splashed with cold water. Throughout the series, more characters are introduced, some with curses similiar to Ranma's, and Ranma and Akane begin to love each other, even though they refuse to admit it.
Anime: Saotome Ranma, a teenage martial artist, and his father Genma travel to the 'cursed training ground' of Jusenkyo in China. There, despite the warnings of the Chinese guard, they fall into the cursed springs. From now on, whenever Ranma is doused in cold water, he turns in to a girl, and a cute, well-built red-head at that. Hot water changes him back into a man again, but only until the next time. To make matters worse, his father engages him to Tendo Akane, a girl who hates boys.

(source: ANN)