Ranma Saotome and his father, Genma, both practitioners of the Saotome school of anything-goes martial arts, fall into the cursed springs of the legendary training ground of Jusenkyo in mainland China during a training mission. Each spring holds a different curse for any who come in contact with its water, all of which involve who or what has drowned in the spring in the past - Ranma emerges from the spring a girl and Genma a panda, both now cursed to change forms each time they come in contact with hot and cold water.

At the end of their training mission, Genma decides to take up residence with his old training partner, Soun Tendo, owner of the Tendo dojo and head of the Tendo school of anything-goes martial arts, dragging a reluctant Ranma along with him. Soun and Genma discuss the arrangements they had made in the past involving Ranma becoming engaged to one of Soun's three daughters in order to combine the two schools and allow Ranma to inherit the Tendo dojo. It's informally decided that he is to be engaged to Akane Tendo, Soun's youngest daughter, and the two must put up with one another - and their engagement - as Ranma and his father settle into domestic life at the Tendo household.