A captured princess just wants a good night's sleep! Shhh... Kidnapped by the Demon King and imprisoned in his castle, Princess Syalis is...bored. When things seem too peaceful in the Demon Castle, the demons investigate and find the princess in a literal bind. Having stolen a gizmo to create alternate dimensions, Princess Syalis uses it to do good in the world. Just kidding! Of course she uses it for her own (and the Teddy Demons') selfish gain. Then, a lightning storm reveals one demon is (predictably) even more frightened of thunder than the princess. Quilladillo goes home for vacation only to discover he has a stowaway in his trunk, but it's not the princess. Just kidding! Of course it is. And then a relative of the princess appears at the castle! What are the demon hostage takers to do...?!
The creator of Sleepy Princess in the Demon Castle graduated from the BUNSEI University of Art. His first serialized series, Nuigurumi Crush, began in 2013 in Weekly Shonen Sunday S and concluded in 2015. Sleepy Princess began serialization in Weekly Shonen Sunday in 2016.