Sleepy Princess in the Demon Castle manga volume 20 features story and art by Kagiji Kumanomata.

A secretly filmed video of life at the Demon Castle embarrasses its occupants. Agave finally confronts her demons - or rather, the Demon King. Then, when Princess Syalis messes with a magical spinning wheel, it’s Poseidon who takes the hit. To rescue the god of the sea, the princess must embark on a deep dive into the history of the spell and... her own family?! Plus, Twilight’s first love revealed! Sort of.