The protagonist, a young girl named Mono, is a lonely girl who was abandoned by her parents despite being the descendant of famous opera singers. She lives quietly in the attic of the theater while being worked like a servant day after day. Until recently, her beloved older sister would always visit her room and teach her opera and dance, but… now she has gone missing. One day, Mono discovers the whereabouts of her sister. Her sister is at “Ishokan,” an isolation facility for those afflicted by the “Shinigami Disease” epidemic. Shinigami Disease is a terrifying illness that turns living beings into picture books, which then “emerge” into monsters, and the nation has given up on finding a cure. “My sister is gonna turn into a monster… No way! I don’t want that!” Unable to sit back and do nothing, Mono visits Ishokan. In order to explore the monster-filled Ishokan and the “World of Trauma” that unfolds within the picture books the girls mutated into, Mono forms a contract with the legendary monster Mel. “Please protect me, Mel.” “Yahaha… I’ll protect you. Let’s get along well, human.” Even knowing that Mel is plotting revenge against humans, Mono is determined to save the only family who has ever loved her…