Genma Saotome is Ranma Saotome's father and the sensei of the Saotome Dojo of Musabetsu Kakutō Ryū karate ("School of Indiscriminate Grappling", more commonly known in the West as "Anything Goes Martial Arts"). During the time when Genma took Ranma on a decade-long training voyage to improve their martial arts skills, he insisted on going to Jusenkyo in China - a place which he believed to be a training ground. However, because of Genma's ignorance of the Chinese language, he did not realize that the ground was unfrequented because it was cursed. Genma realized all too late the mistake he made, after his son knocked him into a cursed spring during this fateful training session.
Genma was knocked into Shonmaoniichuan (熊猫溺泉 Xióngmāoníquán), the Spring of Drowned Panda. Due to the nature of the Jusenkyo curse, a victim who falls into the spring is cursed to turn into who or whatever drowned there when doused with cold water. Thus, whenever Genma is splashed with cold water, he becomes a giant panda. Hot water, as with the rest of the Jusenkyo-cursed characters, can change him back into human form.
Despite the fact that he and his son were cursed, Genma still brought Ranma back to Japan to fulfill a marriage engagement with his longtime friend and fellow martial artist Soun Tendo, the terms of which were as follows: Ranma would marry one of Soun's daughters and carry on the Anything Goes School of Martial Arts.
Genma and Soun decided that Soun's youngest daughter Akane would one day marry Ranma after Akane's sisters made the ruling on their own — against their will, at least at first. Genma currently resides in the Tendo Dojo along with Ranma, in the hopes that one day Ranma and Akane will get married and fulfill the agreement made by the two families. He spends most of his time playing Go or Shogi with Soun, although he briefly had a job at Dr. Tofu's clinic.
Unlike Ryoga, Mousse and Shampoo, Genma automatically regains his clothing when shifting back to normal, despite being too large to keep them in cursed form. The only other characters who shares a similar trait is Pantyhose Taro. Occasionally, primarily in the earliest stories, the top half of Genma's gi and his glasses will also remain on him when he turns into a panda.
Genma follows his own interpretation of the Anything Goes Martial Arts code, which isn't exactly all that virtuous itself to begin with. Though he himself claims to be a model martial artist, and makes a point of telling Ranma about the right thing to do, it is evident that he does not practice what he preaches. He mostly concerns himself with food, generally looks out for himself, and is an occasional coward when it comes to confrontations with Happosai. While he has his bad moments, such as tying up his wife, stealing Ukyo's dowry or Ranma's dragons-whisker, despite that his son would go bald without it, he is not consistently dishonorable and not remotely evil, but he has attempted to justify mistakes through pleading or ridiculous logic, and tried to flee from or ignore the problems he has wrought. However, he did dedicate 14 years of his life for his son's progress into a martial arts prodigy. In short, he does have a sense of honor, but is definitely willing to bend the rules more than the average martial artist.
Despite being cursed, Genma actually seems to like his panda form and freely goes about in public in it. He regularly uses it in attempts to circumvent attention when in danger of being taken to task by others. If he cannot avoid the problem, he often foists the obligation onto Ranma, which usually creates even more chaos. Although pandas cannot talk, Genma is able to communicate his thoughts while in this form by writing on wooden signs (more constantly in the manga), which he sometimes uses as weapons when he is annoyed with his son. In the anime he was once shown as able to produce enough of them to construct an entire boat.
When his wife Nodoka visits, he turns into a panda in an effort to hide his and Ranma's curses from her. In this situation, he is known as Mr. Panda and is Ranko's (Ranma's female form's alias to Nodoka) pet. Nodoka has seemed far more fond of Ranko than of Mr. Panda. When both of them were sick, she fussed over Ranko, while merely commenting that Mr. Panda had warm fur. Another time, when she was helping Ranko cook dinner, she fed the inedible foods cooked to Mr. Panda. Nodoka has also consistently been shown as completely unconcerned about whether her husband is alive, dead or present, in contrast to her extreme worry about her son. All of this has rendered Genma extremely jealous, once to the point of briefly being willing to take petty revenge by risking to expose Ranma's curse. His panda form was also briefly given the nickname Kumahachi, when a young boy named Yotaro discovered him and took him in as an incredibly pampered pet.
Genma consistently enjoyed being stronger than Ranma during their training trips, since it allowed him to claim most of the food, but was disturbed when Ranma recently passed his prowess in regular fighting (without special techniques), and the latter used the opportunity to repeatedly severely beat him up. However, beyond dedicating one and a half decade of his life to teaching Ranma, there have been a few occasions when Genma has been shown to care about his son. A story in the later part of both the manga and the anime shows Ranma training for a fight against Genma. While he is sleeping, Genma comes and covers Ranma with a blanket much like a father tucking in a small child, which his son found touching, although he referred to it as part of psychological combat. And while helping to teach him the Body of Ice necessary to perform the Hiryu Shoten Ha, he wept genuine tears of regret for having to show very embarrassing photographs.
Genma's tendency to think both only in the short-term and in regards to himself alone is perhaps the primary sticking point in their relationship, with Ranma begruding all of the trouble he is forced to endure because of Genma's mistakes.
As a former student of the grandmaster martial artist Happosai and the founder of the Saotome-Style Anything Goes Martial Arts, Genma is an extremely proficient martial artist. He regularly trains with his son Ranma, who is even superior to Genma in regular combat, but he managed to spar on a roughly equal footing until the "Dragon's Whisker" and "Cradle of Hell" storylines. (In the second mention Genma officially admitted that Ranma had surpassed him) While Genma is usually too lazy or cowardly to show it, his full arsenal of special techniques would make him one of the most powerful fighters in the series if he ever used them in combination.
Though he looks unhealthily hefty, especially in his cursed form, Genma is actually in extremely good shape. Like his son, he has great physical strength, enabling him to punch others a great distance or easily shatter boulders. He possesses enough speed to have kept up with Ranma for some time even after the latter's supersonic Amaguriken training. Genma is also surprisingly agile, capable of powerful leaps. Despite his girth and age, he can withstand great impacts without damage, like falling hundreds of meters into solid stone. His panda form is stronger still, and even seemed to make Ryoga Hibiki exert a certain degree of effort to restrain him during the final storyline.