Minakami Yuki♀

Yuki is the protagonist of the "Down the Rabbit-Hole I & II" chapters. She is a habitual truant with a taste for cigarettes who considers herself antisocial, but in fact has an aptitude for getting along with other girls (and for intimidating boys as well). Besides that, Yuki is a fan of classical literature and she spends much of her time reading on the school's rooftop. As a result of her grandfather's stewardship of a kobudo dojo, she became skilled in ancient form of martial arts.

[Edited from Wikipedia]