|Race:||Beastkin (Dog, Golden Retriever Breed)|
|Relatives:||Unnamed Mother |
|Material Collection Information|
Yui is Kei's younger sister, and she is the youngest of her family.
Yui made her first appearance in A and K in chapter 25. It was explained that Yui and her sisters, Mai and Rie would often make Kei's life 'miserable'. Like her mother and brother, she is a golden retriever breed. Kei seems to be on good relations with her, as he often receives letters from her and the two send mail back and forth often. It is unknown whether Yui keeps in touch with the rest of her family.
A and KEdit
Yui first appears in chapter 25. She mentions her business as the reason why she's in town. Whether she is just an employee or an owner of a business was not made clear. Yui made mention to Kei that she felt 'weak' when her store was robbed. She tells Kei she wants to at least learn self-defense. It is said that Yui was the smartest out of all of them, because she got a job because of how smart she was. She quietly left stating she would be back after her business was finished.
At the end of chapter 26, it was revealed that Yui had been taken hostage, along with others, while at her meeting. Why she and the fellow people in the building were targeted however, was not revealed. In chapter 27, Michel, using the 'Hound Dogs' as pawns in his little plot to drive Kei crazy, took Yui and her business associates hostage. Michel planted a bomb and forced Yui to hold on to it. When Kei reached Yui, he instructed her to take her shirt off, and Kei disposed of the bomb.
Yui, now instructed to take an unspecified time off after what she went through, now lives with Kei. Yui quietly lives in their house, and while Kei was gone, Yui taught Alexandria how to swim and even took Athena, Aria, and Alexandria to a water park she owns. Yui and Alexandria had fun. Yui seemed delighted over her sister's decision to learn self-defense, and looked forward to Rie joining her at Kei's home. Yui and Rie had their first big argument of the series in Chapter 76, when the two took exception to each other's comments.
Kei had Yui and Alexandria pair up in order to separate Yui and Rie. Yui instead took Alexandria to an amusement park she owned. There, Yui introduced Bianca, who was the manager of her park. After receiving the money from the park, Yui gave some back to Bianca in order to make her employees more comfortable when they needed a chance to relax. When Yui met Rie after returning from the park, she apologized. However, Yui learned of her mother's vanishing and rushed off with the others to find out what was happening.
At her parent's home, Hitomi reappeared and handed of Yui's weapon, a Bo staff, for her to use. The weapon's name is ‘Arbitratrio pollentia: Hitoshi’. What the weapon is fully capable of is not yet known. Yui began using her weapon against Saki in her first battle.
Yui was diligent in her schoolwork and would become the 'business dog', as Kei coined it. Yui is responsive to other people's needs, as shown in chapter 28, when she gave up her tickets to Shigure and Kei. At one point in her school life, her mother sent her on a small vacation to live with Kei and Lexi. In order to help her with her vanity issues, Lexi and Yui walked around naked around Kei's home (Kei was bedridden due to allergies).