Yuuko Aioi


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Japanese Name: 相生 祐子
Romanized Name: Aioi Yūko
English Name: Yuuko Aioi
First Appearance: "Nichijou Episode 0"
Affiliated: Mio Naganohara (friend)
Mai Minakami (friend)
Nano Shinonome (friend)
Hakase (friend)
Mother Aioi (mother)
Japanese VA: Mariko Honda

Yuuko Aioi is an energetic high school girl with short brown hair. One of her negative sides is that she is often too lazy to do her own homework and always copies from either Mio or Mai. Her nickname is Yukko (ゆっこ).


Yuuko's Fashion
Yuuko has short pale chestnut-brown hair, dark-umber eyes, and wears various home clothes, and the schools standard girls uniform. As seen in flashbacks, she has seemingly always had the same appearance since she was a little girl.


Yuuko loves making jokes and other people laugh, but often fails with her jokes or delivery. Yuuko is usually undeterred by her failures to crack jokes and is creative with coming up with new jokes or humorous reactions. Yuuko loves it when other people laugh at her jokes, but this is far and rare. She tends to be clumsy, and takes a simple-minded approach to life. She is not academically inclined, not diligent with her homework, and tends to fail tests.

Yuuko house

Yuuko's home

While she is generally an easygoing person, her mood changes instantly if she is insulted. She sometimes speaks Malay by greeting others with a selamat pagi which means good morning in both the Malaysian and Indonesian languages. Yuuko is shown to have a fear of snakes, and tends to freeze up easily when faced with something she does not understand, but refuses to acknowledge it.


Middle School Yuuko

Yuuko when she was in middle school

  • Yuuko is constantly persecuted by bad luck regardless of whether or not her laziness was a factor. This trait is occasionally emphasized by the appearance of a mysterious dog which puts his paw on her back trying to comfort her after an unfortunate event.
  • Yuuko's "classroom dream" (which is some sort of mini-story that Yuuko dreams about when she falls asleep during classes) is the premise of the Nichijou PSP video-game.
  • In moments of depression, Yuuko comes up with poems related to her present situation. This typically results from being forced into the hallway for disrupting class.
  • When she was in Elementary School, Yuuko wanted to be a frilled-neck lizard.
  • Yuuko's name means "blessed child", with 祐 (yuu) meaning "divine aid; divine grace" and 子 (ko) meaning "child." It also may be a pun on 悠 (yuu) which means "leisurely."
  • Yuuko is 16 years old, Capricorn. Her blood type is A-.
  • Yuuko owns a cat named Magu.
  • In the manga, Yuuko is one of the few people aware of Sakamoto's ability to speak thanks to Hakase's scarf, something which still never fails to amaze her.
  • She's precisely 48 cm taller than Hakase.
  • Yuuko is the only one in Trio Sucharaka whose name does not start with M.


  • "Super Ultra Great Delicious Wonderful Bad"
  • "Just kidding" (なんちゃって - nanchatte)
  • "Doppio?!"


Mio Naganohara

Mio is the closest friend to Yuuko, but they are almost opposites in every way. This causes some tensions between them at times, but they usually appreciate each other's company. Even though Mio tends to be condescending and forgiving with her, some of Yuuko's actions occasionally (and almost always unintentionally) lead her to furious outbursts. Yuuko, on the other hand, is often prone to cheer up Mio and/or praise her for her qualities when the time comes. Mio sits in front of Yuuko in class.

Mai Minakami

Yuuko is usually oblivious to Mai. Whenever Yuuko tries to make Mai laugh, Mai responds nonchalantly. This causes Yuuko to try to make up for humor deficiencies. It is shown in the Manga that Yuuko has known Mai since middle school.


Nano is quite close to Yuuko, even though the latter isn't very smart. Yuuko's imagination was originally the only thing that led her to believe she was a robot because of the wind-up key on her back, but Yuuko only liked Nano more because of it: Indeed, she finds the fact that Nano is a robot to be amazing. Although she knows that Nano is a robot, she never tells anybody about it.


Thanks to her easygoing personality and love for robots and "cool things" in general, Yuuko obtains Hakase's friendship almost instantly as soon she enters the Shinonome Laboratory. Hakase is always estatic when Yuuko comes to visit, and will often fight to ensure she does not leave.

Character songs

Image Gallery

Yuuko's Image Gallery

Nichijou characters
Trio Sucharaka Mio Naganohara · Yuuko Aioi · Mai Minakami
Shinonome Laboratory Hakase (Shinonome) · Nano Shinonome · Sakamoto
Faculty Principal Shinonome · Kousuke Oura · Izumi Sakurai · Manabu Takasaki · Kana Nakamura · Tomioka · Akagi
Class 1-O Yuria Sekiguchi · Makoto Sakurai
Class 1-Q Mio Naganohara · Yuuko Aioi · Mai Minakami · Nano Shinonome · Haruna Annaka · Tanaka · Tsuyoshi Nakanojou · Ogo · Midori Ōmama
Class 2-A Ogi
Class 2-P Kenzaburou Daiku · Koujirou Sasahara · Misato Tachibana · Weboshii · Fe-chan
Others (females) Yoshino Naganohara · Mihoshi Tachibana · Tamamura · Princess Starla · Yuuko's Mother · Double Cheeseburgirl · Sumika · Tanabo · Kimiko
Others (males) Hajime Sakurai · Mi-chan · Dolph · Nakanojou's Father · King Albert · Fey Kingdom Soldiers
Others (animals) Buddy · Karasu · Oguri Cap . Pyon