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 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... (sources from wikidrama)
Half a year has passed and Shirokin Gakuen has closed down. Yamaguchi Kumiko (Nakama Yukie) finds herself a teacher of a few young kids who don't really benefit much from her style of teaching. Through some twist of fate, she is offered a job as a teacher in Kurogin Gakuen. She becomes the teacher of a delinquent 3D class which make her previous students look like angels. In order to protect her job, she must again hide her true identity — the fact that she is the 4th generation of the Oedo Family, a prominent yakuza group... (sources from wikidrama)