Sukami Kyouichi and his older sister Hanaichi come from a long line of exorcists. Both are accustomed to fighting ghouls, ghosts, and monsters, but when Kyouichi angers an actual god, it's Hanaichi who pays the price and mysteriously goes missing. While searching for her, Kyouichi meets Chloe Kowloon, a grim reaper who claims to be Hanaichi's friend. Chloe promises to tell Kyouichi anything she knows if he will help Chloe retrieve her lost memories. But the only way to do this is to complete the "Ghost Diary" -- a notebook belonging to Hanaichi with knowledge on defeating any supernatural being. Can Kyouichi and Chloe finish the diary, or will its subject matter finish them first...?