Nanami is depicted as a gentle and soft-spoken girl who seems weak, but she is actually very strong. However, she is downright terrifying to face during a fight. She displays a critical lack in basic human understandings much like Shichika did early on in the series.However Nanami's disregard for basic human values is even more severe than Shichika's, possibly due to her father trying to kill her. She also flashes very creepy and dark smiles on occasion, hinting to a bloodthirsty nature that lies beneath her fragile exterior. As the seasons go by, her inner murderer gains more sway and she becomes noticeably insane and even fatalistic, in part due to the increasing suffering her body is undergoing. Deep down, all she wished for was to perish peacefully by learning Kyotōryū through her main ability "Perfect Observation" without being taught the technique, which could also take away her strength little by little.
Nanami is a slender girl who resembles her mother Migiri, with long dark green hair that is decorated with pink markings of cherry blossoms and purple eyes.
After leaving the island, she changes into her monk-like outfit of black and purple monk sashes, silver armbands under her long black sleeves, white/mint green stockings, a pink choker, and slippers.
Nanami had fought Shichika only once, which ended in a draw because of her body's condition, and is stated by Shichika to be even stronger than Hakuhei Sabi.
Nanami sees Shichika and Togame off the island as they leave for their journey.
The members of the Maniwa Insect Squad (Kamakiri Maniwa, Chōchō Maniwa and Mitsubachi Maniwa) are sent to the island to kidnap Nanami with plans to use her as a bargaining chip against Shichika. Despite the best efforts of each, she brutally kills them one by one. As per Mitsubachi's request, she buries their corpses with their comrade, Kōmori Maniwa. Soon after, she leaves the island.
During Nanami's travels, she killed off the Itezora clan and the reason is never entirely clear, but she may have been after the sword Soutou Kanazuchi or simply "up-rooting some weeds" as she says to Shichika when they face off.
Nanami comes into possession of Akutō Bita after killing off the people in Shireizan. The katana is later seen stabbed into her chest, which forcibly heals her physical weaknesses. She later confronts her brother and asks him to kill her so she could die and be free of her persistent suffering, a harsh side effect of Migeiko. This proves to be impossible due to her unnatural superhuman strength and unbeatable eyes. In the end, she's killed by her brother, granting her the death she always wanted.
Despite not being taught her family's fighting style, she has keen senses, fast reflexes, and the ability to think ahead, as she had observed her brother during his training and is shown to have used Kyotōryu when attacked by the Insect Squad. Her unique ability is Higi: Migeiko (Hidden Move: Sight Training), which allows her to copy the strengths of those she fight. If she sees a technique once she can imitate it, twice and she masters it, and can combine it with any other moves she has learned. This can also apply to things like the monstrous strength of the Itezora clan, which isn't really a technique but an inherent characteristic of the Itezora, but she somehow absorbs it anyway after massacring the entire clan. She also has an unnatural ability to recover from serious injuries and poisons. However, her bad physical condition limits the amount of time she can fight at full power.
- Kyotōryū: She spied on Shichika and Mutsue training for many years. Because of this, she mastered Kyotōryū, even without her father's direct guidance.
- Kyotōryū: "Red Poppy" and "Daphne" hybrid striking technique - This technique allows Nanami to take all weight out of its enemy and her blows, making it possible to kill her opponent 272 times before it hit the ground. She invented it by adapting Ninpō: Ashigaru by killing Chōchō.
- Hidden technique: Migeiko (見稽古) - Nanami Yasuri was born with the eye of gods, with this ability, she is able to see through any technique, any movement, any weaknesses, thus mastering any ability with observation.
- Ultimate technique: Akutō Nanami (悪刀七実) - This technique requires Akutō Bita, once the sword is stabbed into her chest, her body forcefully removing any injuries or weaknesses from the body, making it's main focus rejuvenation.
- Ninpō: Tsume Awase - This technique allows Kamakiri to lengthen and strengthen his nails into powerful claws.
- Ninpō: Ashigaru - This technique allows Chōchō to make his body weightless, thus increasing his speed and rendering him difficult to hit. He can also use it to skate on water even with the additional weight of both Kamakiri and Mitsubachi on his shoulders.
- Ninpō: Makibishi Shidan - This technique allows Mitsubachi to launch small caltrops that are hook-tipped to make pulling them out impossible and poison-tipped to immobilize his enemy so that he can get in close and kill them with his katana.
- Immense Speed: With the Akuto Bita in her possession, she is able to dodge many attacks Shichika throws at her, enhanced by her other ability, Migeiko.
- Superhuman Strength: As she murdered the entire Itezora clan, she had learned and mastered everything that she saw.
- Ultimate Battle Analysis: Thanks to Migeiko, Nanami can literally predict the attacks of any martial art just by seeing the stance (kamae) that her opponents use. For this reason she declares that stances are pointless and never takes one herself
- The name Nanami means "seven" (七) (nana) and "fruit, good result, truth" (実) (mi).
- Nanami's surname Yasuri means "file, rasp" (鑢).
- Her full name literally means "Seven Fruit Rasp" altogether. Her father's name, Mutsue, partially translates to "branch", symbolically making her the product of the tree that is Kyotōryū.