Soun Tendo has received a postcard from his old friend, Genma Saotome. In it, Genma mentions that he will bring Ranma along with him. Immediately, Soun excitedly looks for his three daughters, Kasumi, Nabiki and Akane, and tells them the good news. Apparently, Ranma will marry one of them, and the two will take over the Dojo. Akane, being the one who hates guys, disagrees, and they start quarreling. Meanwhile, some where else, a red-haired girl with a pig-tail is having a disagreement with a panda, much to the surprise of passer-bys. They start fighting, and the girl is knocked out by the panda...

Back at the Tendo Dojo, a commotion is heard outside. The girl and panda seen earlier rush in, much to the surprise of the Tendo family. Then the girl introduces herself as Ranma! Akane makes friends with her, and decides to have a friendly match with her. Akane losses, but doesn't really mind because the opponent was a girl. After the match, however, a middle-aged man has appeared from nowhere, and Akane meets a guy she has never seen before in the bathroom, when only Ranma was supposed to be inside! What's happening???

The truth soon comes to light;Ranma is actually a guy, and the middle-aged man is his father. While on a training trip in China, the father and son fell into two of the Cursed Springs, springs that turn the next person who falls in it whoever or whatever drowned there last. Genma fell into Xiongmaonichuan, or Cursed Spring of the Drowned Panda, and Ranma fell into Nyannichuan, or Cursed Spring of the Drowned Girl. Apparently, hot water allows them to return to their original form, whilst cold water causes them to change to their cursed form. With this settled, Nabiki and Kasumi decide Akane should marry Ranma, since she hates guys so much and Ranma is only "half-guy"!

It is then arranged that Ranma shoud go to the same school as Akane. On the way to school, the two teenagers meet Dr. Tofu, the Tendo family doctor. Ranma realises that Akane likes Dr. Tofu. Upon reaching the school gates, Akane and Ranma are surrounded by a horde of guys wanting to defeat Akane. Akane defeats all of them easily. Then another guy comes. Tatewaki Kuno is his name, and he is the cause of all this mess. He has announced that Akane will not date anyone that cannot defeat her, and this has caused Akane to be late for school everyday. He starts fighting with Ranma, but it suddenly starts raining. Ranma, of course, runs off, but only after his father beats Kuno up.

Worst still, Kuno is incensed when he learns of Akane's engagement to Ranma, and rushes off to find him in the middle of class! Ranma leads him on a chase, then jumps right into the swimming pool! Ranma frantically runs away to hide, and meets Kuno before he can change back! This causes Kuno to like Ranma, and he even tries to date "her"......