There are some teachers who are beloved—special individuals who make school a warm and welcoming place, and who are always happy to listen to students' problems. Nanami Takao strives to be that type of teacher; however, her students see her in a completely different way.
Wanting revenge on Nanami for her supposed part in the death of a good friend, Kaede Kanda and the rest of Kamishiro High School's Class 2-A present themselves as model pupils, while secretly plotting to get rid of their teacher. They decide to have a classmate, Miyata Masaru, fake his suicide and implicate Nanami as the cause of his suffering. At least, that was the plan, until Miyata actually dies.
But Miyata's mysterious death is just the beginning of the tragedies that befall Class 2-A, as this event causes a chain reaction of vengeance that may leave no one unscathed.