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.
Hidden technique: Migeiko (見稽古) - Nanami Yasuri was born with the eye of gods. This ability allows her to copy any technique, movement and strength that she sees. If she sees a technique once she can imitate it, twice and she masters it. Her eye of the gods also apply to inherent characteristics, such as the monstrous strength of the Itezora clan, which she was able to copy after massacring the entire clan, despite it not being something that can be learned naturally. Nanami can also combine the moves that she has learned in order to create new techniques, allowing her to adapt and grow extremely fast.
- 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.
Enhanced Strength: Due to her Migeiko, Nanami was able to copy the Itezora clan' inhuman strength. She is capable of cutting people with her bare hands.
Enhanced Speed and Reflexes: With the Akuto Bita in her possession, she was able to dodge many of Shichika's attacks. With the help of her Migeiko and Ultimate Battle Analysis, Nanami can predict her enemies movements with extreme accuracy.
Enhanced Recovery: Nanami has the unnatural ability to recover from serious injuries and poisons. This ability has allowed her to survive and reach adulthood, despite her frail body.
Ninja Arts: After fighting the Maniwa Ninja Corps, Nanami has managed to learn multiple of their ninja techniques through the use of her Migeiko.
- Ninpō: Tsume Awase - This technique allows Kamakiri to lengthen and strengthen his nails into powerful claws. Nanami learned this technique from him and killed him with it.
- 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. After learning this technique, Nanami created the Kyotōryū: "Red Poppy" and "Daphne" hybrid striking technique.
- 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. Nanami managed to copy this technique, allowing her to hit Mitsubachi with one of his own caltrops.
Kyotōryū: Despite not being taught her family's fighting style, Nanami has managed to learn the martial art by spying on Shichika and Mutsue training for many years and using her Migeiko. Because of this, Nanami has mastered Kyotōryū, despite not having her father's direct guidance.
- Kyotōryū: "Red Poppy" and "Daphne" hybrid striking technique - This technique allows Nanami to take all weight out of her enemy and her blows, making it possible to kill her opponent 272 times before they hit the ground. She invented it by adapting Ninpō: Ashigaru which she learned by killing Chōchō.
Ultimate technique: Akutō Nanami (悪刀七実) - This technique requires Akutō Bita. By stabbing the sword into her chest, her physical limitations are removed allowing her to overcome her weak constitution and fight with her full power. She also gains a healing factor that allows her to heal from injuries more quickly.
Akutō Bita: One of the twelve Deviant Blades. By stabbing the blade into one's chest, Bita electrocutes them and forcibly removes their body's physical limits. This grants them a powerful healing factor and immense physical strength.
Swordless: Due to being a member of the Yasuri family, Nanami is unable to use a real sword.
Weak constitution: Nanami was born with an extremely frail body, handicapping her potential and physical strength. However after acquiring Akutō Bita, this weakness was removed allowing her to fight at full power.
Deviant Blade Poison: As the wielder of a Deviant Blade, Nanami is affected by the "poison" that exists within the sword. This "poison" makes her unwilling to give the sword away.
- 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.