When the bizarre mass suicide of 54 high school girls throwing themselves in front of a subway train appears to instigate a string of suicides around the country, Detective Kuroda strives to find the answer, which isn't as simple as he had hoped.

A teenager named Noriko Shimabara runs away from her family in Toyokawa, to meet Kumiko, the leader of an Internet BBS, Haikyo.com. She becomes involved with Kumiko's family circle, which grows darker after the mass suicide of 54 high school girls.