The story of a young, idealistic teacher who enters Shirokin Gakuen with hopes of making a difference in the students' lives. However, Yamaguchi Kumiko (Nakama Yukie) is in for a rude awakening when she finds that she will be the homeroom teacher of 3-D, the hardest class to maintain in the school. The students have multi-colored hair, sloppy uniforms, and show absolutely no respect to her. The leader of the class, Sawada Shin (Matsumoto Jun) is lazy but bright and shows some interest in Yamaguchi when he notices that she is very different from other teachers. The students try to bully her to make her quit, but their attempts don't get them very far.

What the class and the rest of the school does not know is that Yamaguchi Kumiko is actually the 4th generation heir to the Ooedo Group, a notorious yakuza clan. Even though her family would like her to take the title of Ojou when her grandfather dies, they have accepted the fact that Yamaguchi would rather be a teacher.

Eventually, the students learn to respect their quirky teacher because of her devotion to them, and even give her a nickname: Yankumi.

Matsumoto Jun as Sawada Shin

Namase Katsuhisa as Sawatari Goro, Kyoto (School Vice Principal)

Utsui Ken as Kuroda Ryuichiro (Kumiko's grandpa / 3rd Generation Oedo Yakuza Boss)

Anan Kenji as Wakamatsu Hiro

Kaneko Ken as Asakura Tetsu

Uchiyama Shinji as Tatsukawa Minoru

Ryogoku Hiroshi as Sugawara Makoto

Oguri Shun as "Uchi" / Uchiyama Haruhiko

Waki Tomohiro as "Kuma" / Kumai Teruo

Narimiya Hiroki as Noda Takeshi

Ishigaki Yuma as Minami Youichi

Itoh Misaki as Fujiyama Shizuka (English Teacher)

Nakazawa Yuko as Kawashima Kikuno (School Nurse)

Nabe Osami as Ando Osamu (Social Studies Teacher)

Kohmoto Masahiro as Iwamoto Kouhei (P.E. Teacher)

Ookuma Ichirou as Oyama Hajime (Science Teacher)

Tayama Ryosei as Shirakawa Gonzou (Principal)

Saito Satoru as Washio Kanji (Japanese Language Teacher)

Sawamura Ikki as Shinohara Tomoya (Police Officer)

Sakata Tadashi as Kashiwagi Yutaka (Police Officer)

Class 3D

Kawai Jun as Kechi Jun

Kou Kouhei as Imagawa Kouhei

Okabe Hiroshi as Uesugi Hiroshi

Kamiji Yusuke as Ooishi Yuusuke

Izumi Masayuki as Oouchi Masayuki

Kanazawa Kouji as Oda Kouji

Matsuzawa Ren as Gamou Ren

Kitamura Eiki as Shimazu Eiki

Sainei Ryuji as Senzoku Ryuji

Tomita Sho as Takeda Sho

Tomita Shigeo as Chikamatsu Shigeo

Sasaki Hitoshi as Hazama Hitoshi

Hatakenaka Masafumi as Hattori Masafumi

Furuhata Katsutaka as Fujiwara Katsutaka

Nishikawa Yuuya as Houjou Yuuya

Nagayama Hiromi as Hosokawa Hiromi

Morimoto Ryouji as Horibe Ryouji

Yashiro Shingo as Maeda Shingo

Onodera Makoto as Matsudaira Makoto

Matsuyama Kenichi as Mouri Kenichi

Nishitani Mitsuru as Yagyuu Mitsuru

Guests

Tanaka Koutaro as Watanabe (student of Ara High School, ep2)

Inoue Keiko as the thief victim (ep3)

Asaka Mayumi as Uchiyama Sayuri (Uchi's mother, ep3)

Fujima Uchuu as Teradomari Yuuichi (Class 3A, ep3)

Ooshima Youko as Teradomari's mother (ep3)

Kurita Riko as Morisaki Ami (Momoyuri Girls High School, ep5)

Wentz Eiji as Yuki Masato (27th student of Class 3D, ep 6)

Otsuka Yoshie as Yuki Masato's mother (ep6)

Sunaga Senjuu as Kumai Masako (Kuma's mother, ep7&11)

Nishioka Tokuma as Sawada Shoutarou (Shin's father, ep7)

Ichikawa Yui as Sawada Natsumi (Shin's little sister, ep 7)

Oki Naomi as Sawada Kyoko (Shin's mother, ep 7)

Tawaragi Tota as Noda Takeshi's father (ep7)

Yamaguchi Shishi as Mouri Kenichi's mother (ep7)

Kobori Haruki as Kawashima Yuuta (ep8)

Maeda Masaki as Kawashima Kikuno's father-in-law (ep8)

Kishiba Ichiko as Kawashima Kikuno's mother-in-law (ep8)

Tsukamoto Takashi as Kurosaki Yuuji (former Shirokin student, ep 9)

Akiyama Natsuko as Sawatari Sachiko (Sawatari-kyoto's wife, ep10)

Higuchi Koji as Ijuuin Toshihiko (teacher in Ei Shou Gakuen, ep10)

Tanaka Kei as Ono (student of Ei Shou Gakuen, ep10)

Musaka Naomasa as Kumai Kazuo (Kuma's father, ep 11)

Yoshihara Saki (Kuma's little sister, ep11)

Fukumoto Shinichi as Tachibana (writer of "Shuukan Wenzudee", ep 12)

Kimura Yasushi as Itou (photographer of "Shuukan Wenzudee, ep 12)

Hiraizumi Sei as Sawatari Kentarou (Shirokin's director & Sawatari-kyoto's father, ep 12)

Matsumoto Rio as Wakaba (Hot Spring's attendant, special)

Kaneda Akio (Uchi's future boss, special)