Gokusen

Gokusen (ごくせん?) is a manga series by. The story follows Kumiko Yamaguchi, the granddaughter of a Yakuza boss and teacher at an all-male private high school. In 2008, a SP manga was out, featuring some of Yankumi's (Kumiko) old students who are by now working adults.

Unsourced

 * Yamaguchi-Sensei
 * - “What’s wrong with me protecting you? If that is not acceptable, I’ll be willing to quit teaching.”
 * - “Your physical strength doesn’t determine how strong you are. If you have the strength to protect what is important to you, that’s all you need.”