Yaya Yuiki (結木やや, Yuiki Yaya) is the childish girl serving as the Ace's Chair and is one year junior to Amu. Yaya often acts immature for her age, such as having an enormous sweet tooth, and a great soft spot for items like ribbons as well as tending to be hyperactive. Yaya wants to be a baby forever, so her parents would give her more love than her younger brother. She is also a good ballerina, but also a rather clumsy one. Yaya's favorite things are cute and babyish.
Voiced by: Tomoko Nakamura
AppearanceYaya wears her hair in pigtails with big red ribbons attached to her hair. Her eyes are brown and her hair is orange/brown. Like the other female Guardians, she wears a red cape at school.
- Main article: Pepe
Her Guardian Character is the infant-like Pepe, born from her desire to become a baby again. Pepe has darkish orange hair in two ponytails like Yaya and light blue eyes. Pepe wears a pink baby outfit with a white bib and a pink and white hat with bunny ears and a red ribbon on the side. Pepe always has a yellow pacifier in her mouth.
Yaya gets a baby bib and a rattle as primary weapon, which can grow to massive size and can be used to perform "Giant Rattle Attack". The attack often ends up failing. In a later episode, she receives a bottle used to perform the "Milk Beam, Strawberry Flavor" attack. Coincidentally, both Yaya and Pepe become very immature during the change. To Character Change, Pepe and Yaya both says "Pretty, Cutie, Love Baby!"
During Character Transformation with Pepe, she becomes "Dear Baby". This represents her desire to be babyish and get attention. The Humpty Lock glitters with purple light.
Her outfit becomes almost identical to Pepe's, including the bunny hat. She also wears slippers.
In the manga, she improvises on her attacks in Chapters 35 and 36 and in the anime of Episode 99 Yaya uses "Merry Merry Double Block" to distract a black dog with two baby mobiles. Then, she uses the command "Duckies Scramble, Go Go" to form a shield of bathing ducks to block the black dog. She later uses "Ducky Dash" to make her ducks all attack the black dog at once, however, that resulted in provoking it. Yaya then uses Duckies Scrum Go Go!! Finally, Yaya uses ""Black Duckies, Go, Go" to turn her cute ducks into seductive ones and attract the black dog, which works.
- Kairi Sanjo: Although it is not fully recognizable, Yaya shows some respect towards Kairi calling him "Chairman" like Amu. She is seen to have cried when Kairi left, and in some scenes the two are close. However, they remain good friends, and their relationship is not extended further. During Shugo Chara! Encore, Yaya and Kairi develop a small crush on each other while setting up the celebration ball for graduation. She later accepts Kairi's offer to return to Jack's Chair once the rest of the Guardians graduate. Kairi, on the other hand, shows little interest in love with Yaya, but this seems to change a bit as seen in Chapter 51.
- Kukai Souma: Yaya and Kukai are seen as being very close when Kukai still attended Seiyo Academy. They were always hanging out with each other alone while Tadase hung out with Nadeshiko/Nagihiko. When Kukai left to go to middle school, Yaya cried and clung to his arm, begging him not to leave. Later, Kukai gave one last hug to everyone, and a small blush could be seen on Yaya's cheeks when Kukai hugged her. Although Kukai and Yaya are more of just "best friends", some people think of them in some kinda relationship.
- Amu Hinamori: Always calling Amu "Amu-chi", Yaya is best friends with Amu. Amu seems to know what Yaya's true self is. She helped baby-sit Tsubasa and teaches her that being an older sister is more of a blessing than a burden.
- Kukai Soma: Best friends, he and Yaya share a few things in common, such as being energetic and hating work. Yaya was upset when Kukai graduated, saying that she did not want him to leave.
- Rima Mashiro: Although polar opposites in terms of outside character, she began to become friends with Yaya after Rima opened up to Amu. They can be seen together sometimes, and their contrasting personalities put them in some funny and awkward situations.
- Utau Hoshina: Even before they actually met, Yaya was shown having deep admiration for Utau because Utau was a super popular singer. Not much is shown for the friendship for Utau and Yaya but in the final battle against Easter, Utau saved Yaya from an X-egg powered dog and together they defeated it. Yaya gains an deeper admiration for Utau during the fight.
- Nagihiko Fujisaki: Nagihiko is actually Nadeshiko, but Yaya does not know yet, however, Yaya became friends with "Nagi."
- Kairi Sanjo: In the manga, Kairi is shown having a crush on Yaya in Shugo Chara Encore! while they are planning a surprise for the graduating guardians.
Since Yaya wants to be considered cute and baby like, she sometimes uses what is called, 'Baby talk,' with her honorifics. This means to take words and make them sound more babyish, for instense, turning, '-san,' into, '-tan.' She also uses '-chi,' as an honorific, although it is not actually a Japanese baby talk honorific, it's just something she made up. Rima seemed rather confused when she first used this honorific around her.
- Her character song is titled "Ookiku Naare!" and comes from the album Shugo Chara! Character Song Collection 2.
- Yaya means a little in japanese.