Clad in her wedding dress, Izumi , a teacher at Seishun High School is found stabbed to death and floating in the school`s rooftop pool. A student confesses to being her murderer to Hibino Meina , class 3C`s president and Goshima, the detective in charge. Noting inconsistencies with their supposed methodology and an incomprehensible motive, this student`s confession is quickly ruled out , only to have another one immediately step forward to take responsibility for the crime. Why are her students claiming to be guilty? And how did she happen to be in her wedding dress?