The remote island suspense horror manga is set in Itsuki's hometown at Sengetsu island. Itsuki left Sengetsu island to attend high school, but returns to the island when his younger sister Mayu gets seriously injured. But upon his return, Itsuki is creeped out by the island's strangely thorough COVID-19 measures, which include wearing a face mask even while eating. One night, Itsuki encounters "something" near his home. What is the truth hidden behind the island's COVID-19 measures? (Source: ANN)