Sakurai Mana

Yuu's classmate - they get along since middle school.
Being unusually gifted, she keeps getting top scores from all exams.
She seems to be unfit for this school, often crossing the borders, which gives lots of headaches to the teachers, making her kind of "problem child" despite her stellar grades. When asked why she chose this school, she replied "Because it was close".
She often speaks like a man, which makes her seem rather unapproachable, but for some reasons she gets along with Yuu very smoothly.
And thus, being class president, she kind of dragged him into role of vicepresident, much to his dismay.