The Legendary Moxibustion of Evil

 is the 125th chapter of the manga and the first chapter of the Ultimate Weakness Moxibustion Arc.

Ranma causes Happosai to get beaten up on one of his daily panty raids and Happosai pays him back by placing a hot ember on his back. The next day on the way to school, Kuno tries to fight Ranma, but Ranma's punches do nothing to Kuno. Kuno beats Ranma easily, followed by a little boy punching Ranma's lights out.

Cast in Order of Appearance

 * Ranma Saotome (male)
 * Happosai
 * Genma Saotome (panda)
 * Nabiki Tendo
 * Akane Tendo
 * Kasumi Tendo
 * Soun Tendo
 * Genma Saotome (human)
 * Tatewaki Kuno
 * Tofu Ono
 * Principal Kuno
 * Mousse (duck)
 * Ryoga Hibiki (P-chan)

Trivia

 * The kanji that is left on Ranma's back from the moxibustion (貧) is "poor", whilst the character 灸 that is on Dr. Tofu's book is "moxibustion".
 * In the Viz Media translation, the cards Happosai distributes telling everyone that Ranma is weak have "Happy Gram" written on them. In the original Japanese version, they simply include the first character of his name inside a circle.