You know when you get splashed with cold water you turn into a girl? wait... maybe you don't... let me explain:

It started in the mountains of China, Ranma Saotome was training with his father at the cursed springs the springs curse is that whom ever falls in takes body of what drowned there last, so Ranma knocked his dad into the spring of cursed Panda, so now when Genma is splashed with cold water, he turns into a panda, and when he is splashed with hot water he turns back into Genma.... taken by surprise at Genma's transformation Ranma falls into the spring of "drowned girl"

Now's when the trouble starts, Ranma doesn't like the idea of turning into a girl every time he encounters cold water... but that isn't his only problem, he has three fianceés! He got Akane for a fianceé because Genma and Soun set up an arranged marriage, He gets Ukkyo for a fianceé because his father, Genma traded Ranma for Ukkyo's father's okinomiyaki cart, but selfish Genma took the cart and ran off, leaving Ukkyo crying on the side of the dirt road behind. Finally Ranma got Shampoo for a fianceé because while training in China he had to defeat her, according to Shampoo's tribe's amazonian rules, she has to marry him, but the man that truly loves Shampoo gets very very jealous of Ranma Saotome!

And Ranma's fianceé, Akane has a pet piglet named P-Chan, whom is really Ryoga, Ryoga has a tempting urge that he will stop at nothing to get Akane to marry him, so Ryoga can take the element of surprise upon Akane by taking form of P-Chan... That is all for this basic introduction to Ranma 1/2