Sleepy Princess in the Demon Castle volume 1 features story and art by Kagiji Kumanomata.

A captured princess just wants a good night’s sleep!

Imprisoned in the castle of the Demon King, all that spoiled-sweet Princess Syalis dreams of is a good night’s sleep! Shhh... Kidnapped by the Demon King and imprisoned in his castle, Princess Syalis is...bored. She decides to while away the hours by sleeping, but getting a good night’s rest turns out to be a lot of work! She begins by fashioning a DIY pillow out of the fur of her Teddy demon guards and an “air mattress” from the magical Shield of the Wielder of the Wind. The princess’s hapless demonic guards soon discover that their captive expects to be treated like, well, a princess. Things go from to bad to worse—for her captors—when some of Princess Syalis’s schemes end in her untimely—if temporary—demise and she chooses the Forbidden Grimoire for her bedtime reading...