It is April at Kokubunkan Public High School which is known for being good at both studies and sports. Aoyagi Haruka, the rookie form teacher of Class 3D, swells with hope. However, the assistant form teacher is Takakura Yuko, the biology teacher with a poor reputation in school. Furthermore, the transfer student Toda Toshio suddenly accuses the class prefect Mochizuki Ryohei and others of bad deeds. There is a lot to sort out for the new school term. One day, Class 3D’s Yamagishi Rio is instructed by her boyfriend, Tatsuya, to collect the email addresses of her friends. Tatsuya attends a first rate university and has also passed the bar exam. He belongs to the “winners”, but is in truth a peddler who sells unregulated herbs. In order to keep her relationship with Tatsuya going, Rio caters to his demands even though she knows is it wrong. Before long, there is a spam email that starts the rumour of Rio offering email addresses and encouraging unregulated herbs. An inspection of Rio’s bag is carried out without warning. Rio seeks Haruka’s help and Haruka promises to keep it a secret from the school. However, Yuko points out that Rio is a mere tool of the peddler. In addition, there is a call about the collapse of the students of Class 3D after smoking the unregulated herbs. In an attempt to save an embattled Rio, Haruka asks Yuko for help. But Yuko coldly says that she will save Rio in exchange for Haruka’s first paycheck. Yuko, the classics teacher Uchida Sumire and art teacher Fujii Aya wear different faces from daytime. They are “black teachers” who solve problems in return for large sums of money.