Happosai, after being foiled by Ranma yet again on one of his panty raids, gets revenge on him by placing a moxa mark on his back, rendering him as weak as a baby. first, Tatewaki Kuno is finally able to defeat Ranma, and then he even gets defeated by a toddler. After going to Dr. Tofu for help, he learns there is nothing he can do to fix it, except if he finds a chart with the moxa locations on the body.
Ranma keeps on challenging Happosai until he learns from a monk that the chart was stolen from their posession by none other than Happosai, who was also about to burn it during cleaning. Ranma gets it away from the flames, but Happosai reclaims it. Ranma, in a last ditch effort, focuses his power and tries to attack Happosai, only to be trashed, even after transforming into is girl form and using his wiles to catch Happosai off-guard.
Dejected, he runs away from the Tendo residence with his father that same night without leaving a word to anybody.