Musabetsu Kakutō Ryu (School of Indiscriminate Grappling) more commnly known as Anything Goes Martial Arts, is a fictional school of martial arts from the anime and manga series, Ranma 1/2. It is the art used by the main character Ranma Saotome as well as his fiancé Akane Tendo and commonly beleived to have been founded by Happosai.

It is most commonly believed that Musabetsu Kakutō Ryu was founded by martial arts master and pervert lecher extraordinaire Happosai during his travels around Japan and China long before the start of the series. How long ago is rather disputed as his exact age has never been disclosed, in the manga, it is sometimes stated that Happosai is 450 years old meaning with his training trip happening when he was still a young man. If this figure is true, then it is safe to assume that the school itself, or at least it's beginnings are quite old. What is known is that sometime before the start of the series, Happosai took two young apprentices, Soun Tendo and Genma Saotome as his students, an act which would lead to both the creaton of the two main branches of Musabetsu Kakutō Ryu, as well as his temporary demise.

After Soun and Genma were able to imprison Happosai in a cave with sake, explosives and a spiritual seal, the two went and foudned their respective branches of Anything Goes, both anemd after their families. Soun would eventually settle down to teach his Tendo school to his daughter Akane while Genma would later take his son Ranma on a ten year long training journey before presenting him to Soun for the eventual reunification of the two schools.

After Soun Tendo and Genma Saotome sealed Happosai, Musabetsu Kakutō Ryu was divided into two school, the Tendo and Saotome schools. Other than this, Happosai also has his own variation, Ganso Musabetsu Kakutō Ryu (Creative Indiscriminate Martial Arts), sometimes mistakenly translated as the Founding School of Anything Goes Martial Arts, though the school itself seems to have beend eveloped to compensate for Happosai's advanced age.

In general, the Saotome school is the more aerial of the two schools with both Ranma and Genma Saotome performing feats of aerial acrobatics during their fights. In this respect, it is probably the closer of the two schools to the original school of Happosai, since the latter also prefers to go to the air when fighting. The Saotome school is also host to a number of offbeat techniques named after animals, such as the "Crouch of the Wild Tiger" which basically invovles prostating oneself before ones enemies. Diversionary tactics such as the latter are hallmark of the Saotome school, the greatest, most secret technique of the school supposedly being running away against overwhelming odds to regroup.

The school also has two sealed martial arts developed by Genma Saotome, the Yamasenken (Mountain of a 1000 Fists) and Umisenken (Sea of a 1000 Fists). Both are schools designed to help in theivery and have some rather deadly attacks. It was in attempting to learn the Yamasenken that the father of Ryu Kumon destroyed their dojo and died, causing the younger Kumon's quest for revenge against the Saotomes.