A man named Genma Saotome and his son, Ranma, travelled to China to train at the accursed Jusenkyo training grounds. The area was spotted with small pools of water with stalks of bamboo jutting from them. Genma and Ranma jumped atop the bamboo stalks disregarding their Guide's shouts and warnings.

Ranma knocks his father out of the air and sends him plummeting into one of the pools below. Ranma is shocked when a giant panda leaps out of the water and proceeds to attack him. The panda gains the upper hand and Ranma falls into one of the springs below. When he emerges he is shocked to find that he has turned into a girl.

The father and son travel to Japan to meet Genma's old friend, Soun Tendo. Even before their children were born, Genma and Soun promised to engage two of their children. Soun's daughters, Kasumi, Nabiki, and Akane are shocked to find one of them has been engaged to a girl, but once Ranma's secret is revealed, the two elder daughters elect Akane to be Ranma's fiancee.

Ranma and Akane can not stand each other after their first meeting. Akane thinks Ranma is a pervert when he accidentally see her nude in the bathroom, and Ranma is not fond of Akane's aggressive outbursts. The two seem to be a match made in hell, and things only seem to get worse once school begins.

Ranma quickly butts heads with Akane's would-be suitor, Tatewaki Kuno, who tries to win her affections on a daily basis. When Kuno discovers that Akane is now engaged to Ranma, he instantly dislikes him. Things become more complicated when Kuno meets Ranma in his female form and instantly falls for the mysterious "Pig-Tailed Girl".