Yūna has narrow, dark eyes, small eyebrows, and long black hair tied back into a pony-tail. Long bangs frame either side of her face. Her clothing, all black, consists of a small bikini top, a pair of leather heels, and black pants with the left leg cut short. A black ribbon, tied around her waist, billows out behind her. Her left hand is covered in a standard black leather glove but her right glove goes up to her bicep and is patterned with skulls. Like Chiyo, she is thin to the point of appearing somewhat anorexic or gaunt, with thin arms, narrow hips, and small breasts.
Yūna seems to enjoy killing, as shown when she teamed up with Chiyo and Hatae to terminate three of Mikogami's Sekirei. Yuna is also described by Sanada as being extremely dangerous and bloodthirsty, alongside Yuna and Chiyo, she is described as being the "ball" in Sanada's "hidden ball trick" that he initially had no desire to use in his fight with Mikogami. Sanada additionally describes Yuna, along with the other two as having the killer instinct that Shijime, Kuzuri, and Kujika lack, and being uncontrollable when she desires to do something, i.e. fight a strong opponent. She appears to be somewhat of a tease, feigning being hurt by Sanada's comments, while smirking and laughing all the while. However, the trio genuinely seem to love Sanada, eagerly tagging along with the man and his "Lovelies" after being revived by Kusano, and clarifying that they show their "love" in many ways, such as biting Sanada's tongue when they kiss.
Abilities and Powers.
Yūna is a weapons type Sekirei, and uses multiple metal strings, described as a "black wire saw". She was fast enough to land a lethal strike on Mitsuki before the other Sekirei could register that she was in danger. She can work in tandem effectively with Hatae and Chiyo, doing so to quickly overwhelm Mikogami's team, and keep pace with Akitsu long enough for Chiyo to land a blow that almost terminated her. While fighting with the other two, she is able to press a casual Mutsu for a brief period. Her Norito boots her powers for a temporary period, as it does for all winged Sekirei.
Prayer: "My Ashikabi's dark omen be swallowed by my pledge of my black wire saw!"
Nothing about Yuna's past is known in detail, although it can be assumed that she was raised by MBI in much the same way as Tsukiumi, Musubi, and other, more prominent Sekirei were, received tuning and training, and was released by MBI to participate in the Sekirei Plan. She also appears to be close with Hatae and Chiyo, indicating a possible history. At some point she met Sanada and was winged by him.
Yuna first appears during the Fourth Stage of the Sekirei Plan held on Kamikura Island, in which her Ashikabi Sanada confronted Hayato Mikogami and his Sekirei alongside Shijime, Kujika, and Kuzuri. Sanada inquires as to whether or not Mikogami is aware of what the "hidden ball trick" is, to which Mikogami snobbishly comments that he understands the term, but imagines that Sanada doesn't. This aggravates Sanada, who remarks that he "didn't wish to use that ball", before three dark-coloured blurs come into sight. These blurs are Hatae, Yuna, and Chiyo, and they set to work after Sanada introduces them, with Chiyo terminating Juusa and Yuna terminating Mitsuki. Taki uses her fog to obscure the vision of the three attacking Sekirei and shield Mikogami, although it proves to be all for naught, as she is stabbed through the back by Hatae, terminating her. Sanada's continued frustration at the three's uncontrollable nature results in the three finishing each other's sentences to flippantly ask their Ashikabi how they're uncontrollable, and Sanada apologizes to Mikogami before Momo is terminated by the three. Akitsu steps in front of an attack meant for Himeko and Mikogami, using her Reverse Icicle technique to repel the trio, and then her Flying Icicle technique to counter Yuna, the three then prepare to fight Akitsu 3 on 1 while glowering at her. Akitsu holds off attacks from Hatae and Yuna, but Chiyo successfully injures her, causing her to fall. Yuna then listens to Mikogami's speech to Akitsu on human nature, as well as how he came to value his Sekirei for how they unconditionally accept him for who he is, acting somewhat unimpressed and surprised along with Himeko, Mutsu, Yuna, and Chiyo, and the others. The three then decide to attack Mutsu, with Hatae commenting to Chiyo that she doesn't see Mutsu as being too much of a threat, seeing as he retired from the Disciplinary Squad, although Chiyo reminds her that the first generation squad was the strongest, motivating her once again. Mutsu easily repels Yuna's attacks without unsheathing his sword, and comments on his policy of not hurting women, which seemingly arouses the trio, and annoys Sanada. The three continue to hound Mutsu, with Hatae and Chiyo arguing who landed the first hit on the swordsman, until Akitsu is winged, and approaches the trio, preparing to use her Norito. Akitsu executes her prayer, and Yuna, along with the others, begs Sanada to kiss them and activate theirs, while Mikogami, Mutsu, and Himeko flee the area. As Akitsu uses her Ice Erosion technique, Sanada warns the three to run, although Hatae is the only one to properly hear him, the three are then frozen solid and seemingly terminated, although emerging and using her Norito terminates Akitsu due to her unique circumstances. The trio are revived after Kusano uses her Norito, and continue to antagonize Mikogami's party and even their own Ashikabi, eventually they are all kissed and activate their Norito. However, the eventual incapacitation of all Sekirei and Ashikabi barring the two that will challenge Miya on Kouten takes Yuna out of the fight before one can start again.
- Sekirei Manga Chapter 152