Yūko Mano

A.D. 2015: A virus has been spreading in many cities worldwide. It is a suicidal disease and the virus is infected by pictures. People, once infected, come down with the disease, which leads to death. They have no way of fighting against this infection filled with fear and despair. The media calls the disease the "Lemming Syndrome".

Three couples are staying at a lakeside cottage with their children. They want them to prepare intensely for a prestigious high school's entrance exam with the help of a private tutor. One night, one of the wives confesses to her husband that she has killed his mistress.