Sleepy Princess in the Demon Castle summary: Demon Lord Tasogare has taken Princess Aurora Suya Rhys Kaymin of the human empire captive in a world where both humans and demons exist together. He demands absolute control over the world in exchange for her release, but humanity is unwilling to comply and instead sends the hero Yuusha Akatsuki to rescue her. While Suya Rhys remains unharmed, she is trapped in the demon castle and often feels exhausted. She struggles to sleep in the castle's unwelcoming environment, which leads her on a comical journey to find comfort and finally get some rest.