Ranma transforms into a girl when splashed with cold water. An Amazon warrior Shampoo, cursed to become a cat, pursues him. Ranma's friend Mousse fights him over fiance Akane amid a panty thief's antics.

Ranma Saotome, the boy who turns into a girl with a splash of water, always has his hands full fending off crazed admirers. One of the most fanatical is Shampoo, a girl from a tribe of Chinese Amazons who tried to kill girl Ranma, was defeated by boy Ranma, and then proposes marriage to him due to her clan's rule. Things get a little crazier when Shampoo falls into a cursed spring and turns into a cat! And even crazier when Mousse, who is in love with Shampoo, challenges Ranma to a battle over...Ranma's fiancée, Akane...? Back at the Tendo dojo, Ranma's dad, Genma, and Akane's dad, Soun, receive a visit from their former master, Happosai. Around the same time, some of the neighborhood ladies find their undies are disappearing... Is Happosai responsible, or is it just a coincidence?