Sleepy Princess in the Demon Castle v01-v16 (2018-2021)

English translation of the Japanese manga Maou-jou de Oyasumi (魔王城でおやすみ).
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 Wind. The princess's hapless demonic guards soon discover that their captive expects to be treated like, well, a princess. Things go from 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...
While waiting to be rescued, Princess Syalis is so bored out of her mind that she just wants to sleep away the time. But the Demon Castle is terrifying...ly uncomfortable! What's a princess to do to catch some Zzz's other than fashion a pillow out of her captors and make an air mattress from a sacred shield? Unfortunately, her many schemes can only try the patience of the Demon King and his put-upon minions for so long...right?