Yuuna has fair skin, blue eyes with a sapphire tint and straight, sapphire bluish-black hair that nearly reaches to middle of her hips with straight bangs that frame her face. She also has strands which reach to her neck.
As a mother, she often wears a long leaf-green buttonless cardigan with long sleeves, a white dress shirt-like blouse with a collar and a blackish grey knee-length skirt along with dark blackish-brown tassel loafers.
When she was a high schooler, she wore her sailor-styled school uniform which consists of a long white sailor-dress shirt with long sleeves and a dark teal green sailor collar with a thick white stripe nearly around the edges. It also has a short crimson red bow connected to the collar. She also wears a dark teal green skirt and is shown holding a black school handbag. Before, her hair was shorter and neck-length.
In the anime, her eyes are coloured a dark warm purple and her hair was a slighter shade of blackish-warm blue. She appears in Shio's hallucinations with scribbles over her face. In Episode 4 of Shio's hallucinations, she has a horrifying look on her face and bright fuschia eyes which seem to glow.
Yuuna is a kind and meek person. Since she was little, she has never been passionate about anything. She has never chosen anything for herself, as her mother chooses her clothes for her and her father chose what school she would attend. Before she was forced into a marriage, she wanted to find someone who would choose her and live a happy life together with her.
Due to the domestic abuse inflicted by her husband, she becomes overprotective of Shio whenever Shio acts on her own and tends to have a lot of mental breakdowns and bipolarity because of the death and abandonment of her parents and how she is forced to endure her husband's abuse. Shio describes Yuuna as a scary person, a sad person, and a kind person.
Yuuna initially lived an ordinary life as a school girl, but her life drastically changed for the worse after an unfortunate encounter with a boy who raped her. After Yuuna began to show signs of pregnancy and it was far too late to abort, her parents confronted the boy's father, where he forced his son to marry Yuuna in order to take responsibility for impregnating her. After the arranged marriage, Yuuna began living in a new house in an unfamiliar neighborhood. Her husband never came home and her parents stopped visiting her, but her mother did call to check up on her every once in a while. Eventually, Yuuna gave birth to Asahi and raised him on her own due to the absence of his father.
On Shichi-Go-San, Yuuna's husband returned home because his father forced him to attend. Her parents also promised to meet her at the festival in order to talk, but later that day, both of her parents died in a car accident along with her husband's father. Yuuna's husband left again and took all of the inheritance money from his father's and both of her parents' deaths with him. Four years later, he returned home after he used up all the money and abused both Yuuna and Asahi because of Yuuna's inability to get a job and earn money. Soon, Yuuna gave birth to Shio, who was noticeably needier than Asahi was, but she also became a symbol of hope for Yuuna and Asahi to protect.
At some point, Asahi urged Yuuna to run away with Shio and he would stay behind so that their father wouldn't try to find them. While Yuuna cried and apologized to Asahi, wishing that he didn't have to stay behind, Asahi didn't mind because she always protected him throughout his life and wanted her to protect Shio, their Moon. He promised to return to them and made a vow with Yuuna.
Eventually, Yuuna found a place for her and Shio to settle in, waiting until the day Asahi returned, but struggled to keep up with paying rent because of her inability to get a well-paying job. Shio noticed that Yuuna was slowly breaking apart and tried her best to cheer her up, however, Shio's attempts at comforting Yuuna were often futile, as Yuuna feared that her husband would find them again and forbade Shio from leaving the house. Yuuna adopted the mentality that she was no good, for she could not get a job and she was stupid but tried her best to go to work even if she didn't want to.
As Yuuna's state was gradually diminishing waiting for Asahi to return so that they could be happy, Shio begged her to take her outside so that she could find something to help fix her, but almost got in a car accident because of it. Yuuna immediately brought Shio back home and scolded her for wanting to go outside because she was afraid of losing her. For the first time in her life, Yuuna slapped Shio but quickly broke down due to the resemblance between her actions and her husband's abuse.
Soon after that incident, Yuuna decided to take Shio outside again during a rainy night and pushed Shio into an alleyway. Despite Shio begging for forgiveness and promising to be obedient, Yuuna stated that she no longer needed her, and left Shio by herself. Later, Asahi returned to Yuuna after her husband died, but Yuuna told Asahi that it was already too late and everything was gone. Asahi then began to search for Shio to reunite their family again. At the end of Episode 12, Yuuna was seen standing in a building to see how Shio and Asahi.
- Shio and Asahi learned their vows from Yuuna.