The young head assistant of the Kuroda family and the only one of the group that is married.

Kumiko "Yankumi" Yamaguchi enters Shirokin High School to become a math teacher. She's assigned as the homeroom teacher for class 2-4, populated by a gang of delinquents.  At first, the class tries everything to rattle her cage, but to no avail. In a short period of time, Yankumi gains the respect of the class. But what the school doesn't know is that she's the heir to the Oedo Group, a powerful yakuzan clan. So while Yankumi struggles to excel in her career as a teacher, she must also keep her yakuza background a secret.<br>
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(Source: Media Blasters)

Michael B. Pollock is an American voice actor, best known as the current voice of Doctor Eggman in the Sonic the Hedgehog franchise, as well as many characters in various anime English-language dubs and video games. He provided voices for the narrator, Raoul Contesta, and Drayden in the Pokémon series, Adon Coborlwitz from Berserk, Meat from Ultimate Muscle, Langston Lickatoad from Viva Piñata, Suikyou from the Ikki Tousen series and Beast in the motion comic adaptation of Astonishing X-Men.

Fresh out of college, Kumiko "Yankumi" Yamaguchi becomes a math teacher at an all-boys high school. Unfortunately for her, she's assigned by the school board as the homeroom teacher for class 3-D, which happens to be the class of delinquent students. When the class attempts to make a living hell out of Yankumi's career, they fail as her persistence and aggression gain her respect. However, little does anyone in the school know that Yankumi is actually heir to the Kuroda Ikka—one of Tokyo's most powerful yakuza clans.
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(Source: Anime News Network)

Note: Chapter count includes 9 extra chapters in Volumes 9-15

Kouzou Wakamatsu