Nagisa Aoi is the main protagonist of Strawberry Panic!. Nagisa transfers to an all-girls school named St. Miator Girl's Academy, the result of her parents traveling overseas for work, whereas Nagisa chose to stay behind. Nagisa ended up transferring to Miator after her aunt, who is a past graduate of St. Miator, the oldest school located on Astraea Hill, recommended she attend. She is voiced by Nakahara Mai.
Nagisa Aoi is an average girl with red hair and red eyes. She wore the junior high school uniform before meeting Shizuma. Nagisa has enrolled to St Miator and wears the Miator uniform which made her a student of St Miator.
She seems to have a peppy personality, which can usually cause her to get in trouble if it gets the best of her. This trait is apparently quite distinguishing, as Amane Ohtori from Spica had commented that the other Miator students remind her of 'caged birds', but that Nagisa is extraordinarily different. One might theorize that she is one of few Miator students not deeply enmeshed in that school's traditions and customs and therefore more free-spirited and more likely to act according to her own impulses, rather than according to expected patterns. She certainly has a gift for energizing her surroundings and the people around her. At the first few meetings Nagisa had with Shizuma, Nagisa quickly noticed when she gazed into the eyes of Shizuma Hanazono, she was unable to move, leaving her paralyzed. Later into the story she develops a strong relationship towards Shizuma; Suggesting the Etoile may be Nagisa's first love.
Other things about her include that Nagisa is easily frightened, making her tremble at even the slightest mention of something scary, especially ghosts. This continues the theme that she tends to be more childish than most of the rest of the students her age. She has a large appetite, especially for sweet foods. Also, she admires others for their artistic abilities. She herself has displayed an aptitude for acting and the piano, both nurtured through interaction with Shizuma. She is a fairly talented actress, being able to take over the lead role of Carmen when Chikaru is injured. One of her weaknesses is French, for which she requires tutoring from Miyuki and Shizuma.
- She bears a striking resemblance to Kaori Sakuragi. Only difference being is their hair color (Kaori's is black while Nagisa's is red) and Kaori's pale skin.