Ranma 1/2. A story of transformations by water. Basically, if you get splashed by cold water, you turn into that thing, and hot water does the opposite. Now, in the Jusenkyo Training grounds, Quinxai region of China, there are several springs of the Jusenkyo Traning ground. In each is a curse. For if you shall fall in one, you become what drowned there several centuries ago. (The cold,warm water thing comes to be like that. Ranma Saotome and his father were on a training mission to China. Genma Saiotome heard of a place called Jusenkyo , a place where the best martial artists trained. He obviously took his son to these mysterious training grounds.While they were there, the "Jusenkyo Guide" tried to tell them about the dangers of the training ground, but the Saotomes, whom didn't understand English, went to train anyway. As you all probably know, ranma Saotome kicked his father into the spring of drowned panda. Much to his surprise, Genma(Panda) came jumping out as a panda, punched Ranma, and Ranma fell into the spring of drowned girl. Both were shocked as the guide continued their training mission.
They then arrived at the Amazon village of Joketzuzoku. There, they saw one of the famous Amazon matches. They watched Shampoo defeat another fighter with her bombari, and become proclaimed champion. Ranma got all exited, and in girl form, challenged Shampoo. Then, Ranma was able to defeat her in a single hit. Amazon laws state that if the champion gets defeated to a woman, it is a great dishonor. So, the now defeated Shampoo gives Ranma the Kiss of Death, or a mark of "I Shall Kill You!". So, the rest of the journey was spent as Ranma and Genma ran like hell back to the Tendo Dojo.
Soun Tendo was (and still is) one of Genma Saotome's good friends. Soun and Genma decreed that a son or daughter of Genma's would marry the son or daughter of Soun's. So, basically, Ranma and one of the Tendo sisters would be engaged. When Ranma and Genma came back to Japan, they were in their Jusenkyo forms. So, when they arrived to the Tendo's household, they scared the Tendos like hell. Eventually, the Tendos learned of their cursed forms and got over it. Now, within the Tendo household, there were 3 women. Kasumi, the most normal of the 3, Nabiki, who loves cash, and Akane, whom hates boys. Obviously, Kasumi and Nabiki stepped aside, and appointed Akane for the engagement. Akane, will and still, hates boys, engaged or not, and stays hateful to Ranma.