Nagi was a youthful woman with a slender figure. She had shoulder-length black hair, brown eyes and shared a strong resemblance to her son Junpei, as their faces are of a very similar structure.
Nagi wore a violet long-sleeved shirt, with black pants that were held up with a light-colored belt.
Nagi was a friendly, laid-back woman who cared deeply for her son. She was eager for him to make friends and took a liking to Yuji immediately.
As a mother, she had some irresponsible tendencies. She was a smoker and drinker who allowed Junpei to skip school if he wished. Nagi believed that her son could take a different avenue than education to be successful in life.
After just one meeting, Yuji recognized that Nagi was a great person.
Nagi, who was returning home from the grocery store, saw her son Junpei with someone else she didn't recognize and decided to come up and say hello. She was then scolded by Junpei, who took her cigarette, telling her once again to stop smoking for the sake of her health.
Nagi then invited Yuji to dinner with them where they all chatted and shared laughs with each other. Nagi even asked Yuji to do a Mononoke, but didn't understand his movie reference, which ended with Junpei cracking up instead. After dinner she fell asleep at the table and when she woke up to find no one around, she wondered if Yuji had already left. Before she could get up, however, she noticed Sukuna's finger and picked it up in confusion, unaware of the danger lurking right behind her: a cursed spirit that had been attracted to the finger.
Her death is not shown but in the documents on the incident, however, it was reported that her corpse was found with its lower half missing, laid in the bedroom with a bedsheet over it and cold packs and ice bags all over her body.
- Nagi's surname contains the kanji for "good" (吉 yoshi?) and "wilderness" (野 no?), and her first name contains "calm" (凪 nagi?).
- Nagi ranked 28th place in the manga's 1st Character Popularity Poll with 571 votes.