If you're looking for anime similar to Sleepy Princess in the Demon Castle, you might like these titles.
Suzuki Iruma, human, 14, one day finds himself taken against his will into the world of demons. To add to his predicament, his doting owner and self-appointed "Grandpa" is the chair-demon at his new school. In order to survive, Iruma must deal with a haughty student who challenges him to a duel, a girl with adjustment issues, and so many more scary beings! Can this ultimate pacifist dodge the slings and arrows that are flung his way? As he struggles frantically, Iruma's innate kindness begins to win over enemies.
While the plots are not exactly similar, both of these shows have a very unique niche genre I would call "wholesome demon comedy" and they are both surprisingly good. Both feature main characters that get kidnapped and learn to live with their situation.
Both are comedies, that that both feature abducted by demons theme. MCs go similar path but with totally oposite way of doing things.
Banished from Heaven, Beelzebub rules over Pandemonium where former angels that turned into demons work. One day, Beelzebub gets a new attendant named Mullin. Beelzebub seems wise and cool... but she's actually a girl that loves fluffy things! Mullin is shocked at this revelation but still tries to get closer to Beelzebub every day. They are surrounded by various other unique and clumsy demons, and in this story might be about the demons giving a certain emotion a name... maybe.
Both focus on a demon-like setting. The female leads are very cute. Very wholesome. Overall they are very similar and pull your heartstrings.
Same calming energy. The protagonists are charming and cute with an army of characters supporting them in good nature.
Yuuko, Mio and Mai are regular high school girls who lead a normal everyday life. However, with bizarre explosions causing random objects to rain down on their heads, lunch turning into an epic battle between girl and wiener, and students riding to school on goats, their lives are anything but ordinary. Meanwhile android Nano spends her days wishing she were a normal human, but keeping house for her creator, the playful and immature child genius Hakase, dealing with talking cat Sakamoto, and trying to keep a hold of her multitude of easily-detachable body parts, her dream is far from a reality...
I'll make clear right from the get go that: the plot, setting, storyline and the majority of the characters are absolutely nothing alike.
But that isn't what "if you liked this, you'll like that" is all about. I believe that if you liked the sense of random style humor and the overall easy watch feel of Sleepy Princess in the Demon castle or the same for Nichijou, you'll probably enjoy the heck out of the other.
Both are hilarious, fast paced and truly endearingly odd.
You may disagree, but I think these 2 are peas in a pod.
Innocent, naive, and locked in the castle tower since birth, Princess Arete wants nothing more than to escape the royal life and live as the commoners live, and to see things that she has only dreamed about in her books. One day, her wish is granted -- though under less than ideal circumstances -- by the sorcerer Boax, who charms her into becoming his wife. On his flying machine from the days of magic, Arete embarks on a mystical journey full of discovery, enlightenment, and wonder beyond belief...
The greatest demon lord in all of history, Varvatos, has reigned for several millennia as an absolute ruler. Now, there's only one thing left for him to do... enjoy the life of an average commoner! When he's reincarnated as a villager in a non-descript town, everything seems to be going as he hoped but there's just one slight problem-even when he holds back, Varvatos is still too strong! Soon, rumors about him spread and he's approached by all sorts of men, women, and assailants! The quiet life he's always dreamed of seems far away indeed...
Second season of The Misfit of Demon King Academy.
Continuation of The Misfit of Demon King Academy 2.
The Seven Deadly Sins may have ended the tyranny of The Ten Commandments for now, but that doesn't mean all is peaceful in the kingdom. Separated from the rest of The Sins, King and Diane strike a deal with former Commandments Gloxinia and Drole, and agree to undergo special training--which sends them to a Britannia 3,000 years in the past, right before the end of the Holy War! Can the pair navigate this strange past--and a threat more powerful than The Ten Commandments?
Only six of the Seven Deadly Sins have been located so far, so our heroes travel to the kingdom of Britannia to find the final missing member of their group. New adventures await them, along with powerful new adversaries: an elite group of demonic warriors known as The Ten Commandments!
After being summoned to another world similar to the game he used to play, Diablo lives a tumultuous life in this new world after he finds himself the unwitting master of Rem the Pantherian and Shera the Elf; and now, even the Demon Lord-turned-young-girl Klem obeys him! One day, Diablo ends up rescuing a holy woman who was being pursued by a Paladin, and she turns out to be the most important person in the Church. Befriending her, Diablo and the others act as her escorts until they reach Zircon Tower deep in the Demon Lord’s territory. After arriving in a new town, more difficulties arise, ultimately culminating in the appearance of a gargantuan monster attacking them! Is the self-proclaimed Demon Lord becoming a guardian deity for a follower of the Gods!?