Yuuko Aioi, also known by her nickname Yukko is one of the five main characters of Nichijou, alongside her friends Mai Minakami and Mio Naganohara, Nano Shinonome and Hakase. She is an energetic high school student with short brown hair. Throughout the series, negative things sometimes happen to Yuuko, even if they logically shouldn't. Yuuko is fair-skinned and has short pale chestnut brown hair with bangs pointed in the middle. Her other part of the bangs which appear on the outer sides are shorter and pointed. Her ends are pointed outwards and has short strands that reach to the middle of her ears. She has dark umber brown eyes and wears her girl's school uniform. Her school uniform consists a pale beige sailor top-like blazer with thin white stripes in the middle and at the end of the blazer with a curved white sailor collar that has a thick pale red stripe nearly around the edges and short pale red bow with a chest pocket at the right side. Her top inner part of her sailor top also has a thick pale red stripe nearly around the edges and has white cuffs at the end of her sleeves. She wears a pale red skirt and has darker red pleated designs on it. She wears it with white knee socks and dark greyish- brown tassel loafers with white soles. She also wears another one of her girl's school uniform consisting white dress-shirt like-sailor top with short sleeves. It has a flat collar with a thick light blue stripe nearly reaching around the edges and wears a short light blue tie. Her sleeves have thick light blue stripes at the top. Her back of her collar is long and curved. She wears it with a navy blue skirt, white knee socks, two bows, and white uwabaki slippers with darker blue tips. She sometimes wears tassel loafers with it. In her character arts, she is shown wearing casual outfits. In her home, she wears a short-sleeved V-neck white T-shirt with a hot pink T-shirt with short sleeves which are slightly longer. Yuuko loves making jokes to make other people laugh, but often fails or takes a joke too far. Yuuko is usually undeterred by her failures to crack jokes and is creative with coming up with new jokes or humorous reactions. She tends to be clumsy and takes a simple-minded approach to life. She is not academically inclined, falls asleep in class, is not diligent with her homework (which she frequently just copies from her classmates Mio Naganohara and Mai Minakami), and tends to fail tests. She is scatterbrained and can find it very difficult to concentrate, going on long tangents and overthinking things. 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. She 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.