From Viz:
Being a teenage martial artist isn't easy, especially for Ranma Saotome, who went through a major transformation on a training mission with his father. After an accidental dunk into a legendary cursed spring in China, Ranma now changes into a girl every time he's splashed with cold water. That would be enough to complicate anyone's life, even without the arranged fiancée who doesn't like him (or says she doesn't) and the constant stream of rivals and suitors for both his male and female forms. What's a half-guy, half-girl to do?