In 1972, Misaki, a popular student of Yomiyama North Middle School's class 3-3, suddenly died partway through the school year. Devastated by the unexpected loss, the students and teachers behaved like Misaki was still alive, leading to a strange presence on the graduation photo. In Spring 1998, 15-year-old Kōichi Sakakibara transfers into Yomiyama's class 3-3, where he meets the peculiar Mei Misaki, who is seemingly ignored by her classmates. The class is soon caught up in a strange epidemic, where its students and their relatives are caught up in mysterious deaths. Learning these deaths have something to do with the Misaki of 1972, it is up to Kōichi and Mei to discover the cause of these mysterious deaths and figure out how to stop it before it puts an end to them.