The Father of Ranma. He turns into a panda when in contact with cold water. Even though he is a master of Anything Goes Martial Arts, he is extremely lazy and generally thinks with his stomach.
He was cursed at the same time as Ranma, falling into the Spring of The Drowned Panda at Jusenkyo while sparring with him, turning into a panda. his arriving at Jusenkyo was only because he had head of it in a brochure, but cannot read a word of Chinese. When he is in panda form, he can't speak, so he uses signs to communicate, usually resulting in some form of comic relief.
Genma is an old friend and martial arts partner of Soun Tendo, whom he lives by. they were instructed in Anything Goes Martial arts by their Master Happosai, who made them endure ttreacherous training to the level they had to seal him away. however, the seal was broken decades later, and Happosai, along with ranma and Genma, stay at the Tendo residence.