The Demon Lord Tasogare's castle is a dark and frightening place, filled to the brim with various monsters. Any soul unfortunate enough to be imprisoned here is sure to be terrified by the horrors within. However, the human princess Aurora Suya Rhys "Syalis" Kaymin is a different case. Rather indifferent to her situation, Syalis worries about one thing and one thing only—sleep. Ever since the demon lord kidnapped her from her kingdom, she has not had a single good night's rest.