Following the passing of her close friend Mari Hanashiro, Arisu Ichinokuro inherits Mari's Mushi, the Morpho Butterfly. These insect-like beings consume people's dreams and thoughts in exchange for supernatural powers. To understand why she was given this Mushi, Arisu embarks on a quest to learn more about Mushi and Mushitsuki. She is assisted by Daisuke "Kakkou" Kusuriya, an agent of the Special Environmental Conservation Executive Office who has been assigned as her bodyguard.