The mystery-drama is set in the oldest town by the shore in Japan, Oiso. Kazuya, an abusive leader of the juvenile gang, grew up with three mates, Tomoki, Shun, and Eita. Together they work at his uncle Ito's construction company after graduating from high school. One day, Ito was found dead in his own backyard and soon it is revealed that he was remarried in disguise to an unfamiliar woman. Shortly afterwards, Kazuya's grandmother, who suffers from dementia, is reported missing... The series of unsettled mysteries leads to the conundrum and secrecy between the quartet coming into view.