Uka Ishimori is introduced as a fifteen-year-old first year high school student who's been dubbed the nickname 'Stone' due to her emotionless face and shy personality.
Uka is a cute young girl standing at average height with a slim physique of 156cm(5‘1"). At the start of the series, Uka is usually seen with her hair down, at which the length falls down to her shoulders, and that her bangs are parted off to the right side. Her eyes are golden in color and her lashes are notably long. In addition to her demure personality, her cheeks are noted to be rosy.
As seen throughout the manga, her hair grows in length, and she wears it in a variety of different styles as she grows more confident in both her appearance and fashion sense. Uka, much like the rest of the cast, usually is seen in her high school uniform, which consists of red bow with blue and white stripes, blue knee length socks, a white shirt, a beige or black jumper, depending on the season, a blue blazer and a red and blue checked skirt that falls just above her knees. Outside of school, Uka's fashion is feminine and soft, often she wears skirts, dresses, blouses and hair accessories.
At the start of the series, Uka is introduced as an extremely shy individual with the inability to express her thoughts and emotions. The reason behind this is due to the fact that her peers, as well as her bullies, would give her the moniker "stone". Because of how incredibly difficult it is for her to say what she thinks or feels, she typically clams up and refuses to say a word. As such, this habit of hers would become the source of annoyance to Kai Miura, who wants her to be independent and gain the confidence to say what she thinks and express how she truly feels.
In light of this, ever since Uka has met Kai and his group of friends, her perspective changes to where - rather than remaining timid and lacking confidence, even if she tends to be shy at times, she becomes more expressive and proactive with self-assurance.
(Source: Honey Lemon Soda Wiki)
