Kureha

"Kureha (紅刃 Kureha?) is a character from the SOUND VOLTEX series." "A quiet and serious girl in class. She’s extremely shy, being poor at making eye contact and having conversations with people. With her good grades, she’s often asked for her notes before tests. She herself finds happiness in these few opportunities of interaction with other people. However, once she holds a sword, her personality completely changes. She transforms into a mad swordswoman, seeking battle."