Ranma ½ is a martial arts romance/comedy anime, based on a manga by Rumiko
Takahashi. Thanks to his idiot father, 16 year old martial artist
Ranma Saotome is cursed to turn into a girl whenever he's splashed
with cold water; hot water will turn him back to a boy, but only until
the next time he encounters cold water. Soon after he's cursed, he
finds out his father also engaged him to a girl he's never met,
much less heard of, and she isn't any happier about this "surprise"
than he is.

And so begins the story.