Soun and Genma trained under the notorious and perverted Happosai during their youth. This small but formidable man is the grandmaster of Anything Goes Martial Arts (Musabetsu Kakutō Ryū). He is infamous for his panty thievery and insatiable lechery. In exchange for training, he coerced his reluctant students into aiding him with his panty raids and peeping activities, often resulting in humiliation or injury for them. Once they completed their training—or rather, managed to escape—they were able to move on with their lives. However, their peace was short-lived as Happosai returned to find a successor.
Upon arriving at the Tendou Dojo, Happosai encountered Ranma, who was in his girl form at the time. Despite knowing that Ranma is male, Happosai shamelessly pursued her. Settling into the Tendou Dojo, he resumed Ranma's training while also expanding his panty raiding activities into the neighborhood and even into the Tendou girls' bedrooms.
Happosai is a diminutive yet incredibly powerful martial artist. He typically wears a purple jumpsuit or occasionally a green bathing suit. During his panty raids, he often dons a scarf as a mask. He is bald with white fringe hair and a white mustache.
As a master martial artist, Happosai possesses deceptive strength for his size. His primary weakness is his perverted nature; he would risk life and limb for a pair of women's panties. Often, he can be thwarted by a well-placed bra, and if he cannot indulge in his lechery, he experiences withdrawal symptoms akin to an addict. His power stems entirely from his lust, making him easily defeated by denying him this source of energy.
Happosai is proficient in numerous magical martial arts techniques, though many are merely special effects. For instance, his feared "Happo-dai-karin" (Happo Fire Blast) technique is essentially just a firework ignited by a match. Nevertheless, he does possess several potent special energy techniques as well.
