Nagisa Aoi is the main character. Nagisa suddenly transfers to an all-girls school called St. Miator Girl's Academy. The reason she transferred is because her parents went overseas for work, leaving Nagisa behind. Nagisa ended up transferring to Miator after her aunt, who is a past graduate of St. Miator, the oldest school of Astraea Hill, recommended she attend.
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 first, whenever Nagisa gazed into the eyes of Shizuma Hanazono, she was unable to move, as if paralyzed. Later on, she develops a strong attraction towards Shizuma; the Etoile may very well be Nagisa's first love.