Oresama Teacher #1, Viz Media

Oresama Teacher Volume 1 - A manga series by Izumi Tsubaki, published by Viz Media under their Shojo Beat imprint.

Mafuyu is a delinquent gang leader with a no-nonsense attitude who gets expelled from her high school. Sent to an isolated country school by her fed-up mother as punishment, Mafuyu is determined to reform and make her mother proud. However, her fighting spirit proves hard to suppress—the night before school starts, she finds herself defending a stranger from a beating. To make matters worse, that stranger turns out to be her new teacher, putting Mafuyu in an impossible position as she tries to become a good girl while her wicked past refuses to stay buried.