Kumiko Yamaguchi, the 23 year old granddaughter of a yakuza boss, becomes a teacher at Shirokin Gakuen, an all boys high school.

After Kumiko saves a woman from a drunk man, she is surprised to find that the woman is Kuma's mother. Kumiko grades math tests and after she learns the class' average is 21 she holds remedial classes, hoping some would come.

After being suspected of stealing, the group including Kumiko, set out to catch the real thief.

Kumiko must be the head of the Ooedo clan while her grandfather is hospitalized. This episode shows some of Kumiko's childhood.

Shin and Kuma see Kumiko get into a car with two people who are part of the Ooedo clan. They follow her to her house but are caught and Kumiko and the clan put on a act so Shin and Kuma won't find out anything. Kuma falls for the act but Shin finds out the truth but promises to keep it a secret.

Ms. Fujiyama tries to get Ichikawa, a good student with bad friends, to join the choir club. Some of Ms. Fujiyama's past as a middle school teacher is shown and how a past student reminds her of Ichikawa.

The class goes on a field trip but things go bad when Uchi is kidnapped. It turns out that they saved the wrong Uchi but luckily they find the Uchi they had been looking for.

The school has a festival and Kumiko's class is having a host club but things don't go well as everyone leaves to go fight the seniors except for Shin.

Many students is school start to wear a cat badge which is worth 10,000 yen so Kumiko decides to check things out. She finds the people selling them but is overpowered when Shin is taken hostage. Then some people from the Ooedo group come and help. The next day Shin is absent from school.

Kumiko learns that Shin's father is going to have him drop out of school and once she learns why, Kumiko decides to try and get Shin to stay in school.

The board of directors decides to close down Shirokin Gakuen but Kumiko won't allow them. The directors decide that if the school can become number one in Japan academically or in sports in two weeks they will not close it down. Kumiko decides to have the school become number one in boxing.

After the vice principal discovers Kumiko's background, she resigns as a teacher. After leaving the school Kumiko is kidnapped and Shin goes after her while Kuma goes to get help from the class. At first they resist but after some convincing they decide to go help.