Prodigy detective Mitsuko Unagi is on the hunt for a notorious serial killer known only as "Eleven". 10 years earlier, on February 29th 2006, a series of murders began, involving 11 randomly selected victims killed simultaneously in various parts of Tokyo. The killings continue over the next decade, leaving the police with no evidence, no witnesses, and the killer always one step ahead. But now something has changed, and the killer has changed his pattern, giving Detective Unagi the one chance to finally get closer to solving the mystery of the Random 11.