Natsume (なつめ, Natsume) is a young woman who is an itinerant martial artist along with her younger sister, Kurumi. For years the two wandered Japan in search of their long-lost father, Soun Tendo. They briefly usurped Akane Tendo and Ranma Saotome’s claim to inherit the Tendo Dojo and carry on Anything Goes Martial Arts after challenging and defeating them, but conceded their claim following a rematch.
Natsume has light brown eyes and long, dark brown hair that she wears back with a high topknot secured with a white tie. Her fringe is parted in the middle and she has two long strands of hair that hang down from her ears. She is taller than Kurumi and about as tall as Ranma in his male form. Natsume typically wears a dark blue short-sleeved school dress with a white sailor outfit-style collar. Her training outfit is a sleeveless, low cut light purple jumpsuit secured by a white sash around the waist. When she was younger Natsume's hair was shoulder-length and held in a ponytail with a white bow. She also wore a similar training outfit that was a medium blue with a black sash.
As the older of the two sisters, Natsume is the opposite of Kurumi. She can be characterized as being colder, and her personality and attacks appear to be associated with ice and wind. More mature, reserved, polite, and ruthless, Natsume notably lacks Kurumi’s voracious appetite.
Natsume was found 18 years ago in a pile of sand near a shrine and was adopted by the priest. Two years later Kurumi was found there as well. Since the two had the same medallion the priest theorized that they must be sisters. So every year he took the two back to the spot in case someone was there. Eleven years ago despite the priest being ill the two decided to go to the spot by themselves when they were attacked by a bear. However they were saved by a passing martial artist, who they believed to be their long-lost father. This stranger, later revealed to be Happosai, told them that when they became true martial artists they would inherit the Anything Goes School of Martial Arts. Two photos were taken of him with the sisters. One, which showed the three side by side, was kept by Happosai. The other, in which only his back was shown, wearing his gi with "Anything Goes Martial Arts" written on the back, was kept by the sisters. On the back of this photo Happosai wrote that they would carry on the school when they were older and signed it as "Soun Tendo", with the intention of giving them a goal to strive for. However he never told Soun about this promise. Since the girls were young at the time, they had forgotten what Happosai looked like and had grown up believing their father to be a heroic, larger than life figure.
Since then, the two traveled throughout Japan, largely living a nomadic existence, although their use of school uniforms suggests that they were enrolled in school at some point. They eventually end up in Furinkan, where, with their money having run out, they resort to a series of food thefts in order to eat. Kurumi’s ribbon comes in handy, and the pair hits Okonomiyaki Ucchan's, Shampoo on a delivery accompanied by Mousse, and later Ryoga Hibiki and Tatewaki Kuno. Because of their speed and Kurumi’s ability to eat any quantity of food in a matter of seconds, the food thieves’ identity cannot be determined.
However they reveal themselves when Akane Tendo is walking home with some food from a local restaurant. Kurumi is ravenously hungry, but Natsume stops her from grabbing the food out of Akane’s hands, allowing her to accept when Akane offers it. They pair then thank her and follow her home, despite her efforts to lose them. In the living room, Natsume stops Kurumi from helping herself to the snacks that Kasumi offers them. After Nabiki comments on their manners, the pair then introduce themselves, Natsume explaining that they were driven to steal food when they ran out of money and now desire to pay Akane back for feeding them. After hearing their story, Soun offers to host them for a while, which they accept.
Akane later learns that the two are martial artists and searching for their father, who they believe to be a powerful martial artist. Natsume readily takes her up on her offer to spar with them, and Kurumi somewhat reluctantly agrees, although she ends up being the one to fight Akane, saving her from crashing into some exercise equipment after dodging a flying kick that Akane loses control of. After dinner, Soun asks how Akane and Kurumi’s sparring match went, leading Nabiki to respond that she was a pushover as Akane is only doing martial arts these days to avoid dieting. When she comments that the heir to Anything Goes Martial Arts is useless, Natsume reveals that their goal is to be the best in what they call Anything Goes Female Martial Arts (Women’s Anything Goes Martial Arts in the dub) to fulfill a promise made to them by their father, Soun Tendo. When Soun reveals that this is his name, the pair calls him father and Natsume pulls out the photo of the three of them together to prove it, as Soun cannot recall ever having illegitimate children. After telling their story, she points out the promise written and signed on the back, which appears to settle things.
Beginning the following day, both sisters begin to spoil Soun and Genma Saotome, preparing their meals, keeping them fed, and even offering to wash their backs while they are soaking in the furo. That afternoon when Genma suggests that they leave the dojo to Soun’s new daughters, Akane disagrees, but the idea is supported by Natsume, who suggests that only the best fighter in the family should be the one to pass on the school, and that she and Kurumi are the more appropriate heirs, not her. After Akane suggests that they see if they are stronger than her, Ranma accepts the challenge in his female form, and Natsume agrees to take them both on.
Prior to the fight, Natsume tells Kurumi not to hold back. After Kurumi beats Ranma back with her ribbon, Natsume hits Akane with a slash that cuts off the left forearm of her gi, following this up with an ice tornado that Ranma has to knock Akane out of the way of. They then finish off their opponents with the Ring of Dragon Fire, although Natsume eased up on the attack to avoid injuring Ranma and Akane. After the latter runs off, Natsume just watches and exults that their long days of wandering were now over.
When Soun discovers where Akane has gone, Natsume asks Kurumi where he is. Later while Natsume is practicing in the dojo, Kurumi speculates that Akane will be returning soon for a rematch. When Natsume vows to fight any challengers, Kurumi suggests that Soun might not be their father. However Natsume is adamant that he is, citing the signed promise on the back of the photo. She tells Kurumi to practice so that they can defend the dojo, and the pair proceeds to punch holes in the wall, which a crying Soun patches up.
On the day of the rematch, Natsume was originally to fight Akane first, but agrees to let Kurumi take her on. She is surprised when Akane puts up good a fight and urges her sister to finish her off. When Akane nearly hits Kurumi with a counterblow, Natsume tells her to trade places, claiming that where one ends, the other begins. However Ranma then appears to make it a two on two fight. Natsume launches an immediate attack by using Kurumi as a springboard. Akane tries to take her but is edged out of the way by Ranma, who is tripped up by Kurumi’s ribbon, allowing Natsume to knock both of them down. However Ranma jumps back to avoid Natsume’s wind slash and jumps over her tornado attack. Pushed back by Kurumi’s ribbon, the sisters then launch their Ring of Dragon Fire attack. In response, Ranma has Akane run into the spiral and fires a horizontal version of the Hiryu Shoten Ha to counter it. This cancels out the Ring of Dragon Fire and propels Akane at the pair, allowing her to take them both out with the Lightning Splits Attack.
Natsume is knocked out, but recovers in time to learn that Happosai was the one who rescued them years ago after he appears and that they were misled all this time. After they kick him through the roof, the pair decide to leave, vowing to train themselves until they are strong enough not to bring shame to Anything Goes Martial Arts, when they will return to challenge Ranma and Akane again.
The two came across Ranko Kuramitsu as she was practicing in the park after initially mistaking her for Ranma’s cursed form. She offered them lunch and when they noticed that the symbol on the back of her jacket was the same as the one on their medallions. When they asked her about it she explained that it was the logo for my parents’ company: Kuramitsu Sol.
Both sisters are stealthy and very fast, which allowed them to steal food from five talented martial artists and escape detection. Their version of Anything Goes Martial Arts has a little bit of what Happosai taught them, but is largely of their own invention. It places an emphasis on fighting together, making them a formidable combination by mutually supporting each other. Natsume specializes in close range fighting, while Kurumi uses her ribbon for distance attacks to set opponents up for Natsume or drive them back. However each sister is a competent martial artist in her own right. It is suggested that Natsume has some hand to hand combat abilities as she can punch through wooden walls, but does not need to rely on it as much as Kurumi, who requires some distance for her ribbon to be effective. Natsume uses a carpet beater as her weapon of choice that she carries on her back for both close combat and ranged attacks, using its design to vary her techniques.