Sushi is from the small town of Japan of Nanporo where her parents own a sushi cafe. She grew up as an only child with her mother and father in a smallish apartment above the cafe, but luckily she didn't have any siblings so that wasn't too much of an issue. 

When she was born, her ears weren't properly developed and she was diagnosed with microtia. This somewhat hindered her in life, where she couldn't hear things properly and she had one ear that was extremely small compared to her other ear, making her halfway deaf. 

Her Mother was the sister of the pro hero FatGum, and from that side of the family they have food related quirks including her Mom. Her Mom had a food quirk, and her Dad had a magic type quirk. So when they found out later in Sushi's life that she had sushi magic, they weren't surprised too much.

She was quirkless most of her life until the age of ten. She lived in a very small town, which meant that everyone knew about it and they picked on her for it. With this she had started learning how to make sushi so that she could work for the family business and her Father saw she did well one day and gave it to one of their customers. This is where they learned that she had developed her quirk, and they were proud of her because they didn't think that she would ever manifest one. 

When she was fifteen, her parents had sent her to live with her uncle FatGum so she could go to high school at UA High, and he lived near there. Plus, her uncle said he missed his niece so it worked out. She went to Class 1D and she there had started her dream of becoming a journalist by signing up for the school newspaper and she got accepted, and there her dream began.