As a teenager, she was mild-mannered and prone to daydreaming. She didn't really make any decisions for herself, and basically just did what her parents told her to. One day, she bumped into a boy by accident on her way home from school, and he yelled at her. In her panic, she said she'd do anything, and the boy ended up raping her, which led to her becoming pregnant with Asahi. The boy's father forced him to marry her and coerced her parents into going along with it. The husband was very aggressive and abusive to Yuuna and young Asahi, but didn't spend much time at home so they rarely saw him. Yuuna gradually became estranged from her parents, particularly her father. Later, just when it seemed like her parents wanted to take her back in, they died in a car crash alongside her abusive "husband's" father. About four years after this, she gave birth to Shio.
The abusive husband wasted a lot of money on drinking and gambling, so Yuuna tried to get a job. Because she had never had to work nor learned the needed skills, she wasn't able to hold down jobs and often got yelled at for her clumsiness. This further amplified her stress, and eventually, she snapped and took Shio out on a walk, leaving her in the alleyway where she was found by Sato. Soon after this, she kills the husband by poisoning his drink.
