Hone ga Kusaru made

The summer they were eleven, they killed a man and buried his body in a cave. Since then, every year, one summer night has marked a ritual: a ritual never to forget, and never to betray. Five years have passed. Their sixteenth summer. The body, now a skeleton. Unraveled lies. A faceless blackmailer. The phone rings and a life is torn apart. The bones, like their crime: never rotting, never fading away. Now, a living hell begins.
(Source: Kodansha USA)