Five years ago, a group of friends murdered a man. Every year since then, Shintarou Nakamura, Akira Kanzaki, Ryuu Nimaidou, Haruka Nagase, and Tsubaki Toyoshima visit the dead man's rotting bones and reaffirm their blood oath to take the secret to their graves.

Soon after one of their yearly visits, the friends hear that a golf course will be built in the area and decide to go back and move the body. Instead of bones, however, they find a cell phone that begins to ring. The group answers it with trepidation, and the stranger on the other end confirms what they already suspect: the bones are indeed missing, and their crime has been discovered. In order to stay out of jail, they agree to do the thief a "favor," and in the process uncover a plot that will test the bonds of their friendship.