Sweet Dreams in the Demon Castle by Kagiji Kumanomata — Ongoing

Also known as Sleeping Princess and Maou-jou de Oyasumi

Epcznjo

The princess of the human kingdom has been kidnapped by the demon king!
But all she wants to do is get a good nights sleep!?

Volume 1
Chapter 1: The Princess in the Sleepless Castle released Jun 25 '16
Chapter 2: Bedsheets Shining Like the Sea released Jun 26 '16
Chapter 3: A Sweet Sleep Known as Death released Jul 25 '16
Chapter 4: Sleeping with the Wind Shield... and Nothing Else released Aug 16 '16
Chapter 5: Because There's a Tower There released Aug 17 '16
Chapter 6: Keep Howling at the Moon released Aug 18 '16
Chapter 7: The Dreaming Poison Mushroom released Aug 25 '16
Chapter 8: The Princess's Three-Star Armour released Sep 1 '16
Chapter 9: But, It's a Heavy Price to Pay, Isn't It? released Sep 9 '16
Chapter 10: Schlaf' ein holdes Kind released Sep 16 '16
Chapter 11: You Won't Go Down Unless You Touch It released Sep 23 '16
Chapter 12: The Sea of Pillows and the Tower of Babel released Oct 2 '16
Chapter 13: Head to the Sacred Treasure Forest! released Oct 10 '16
Volume 1 Extra released Jun 28 '17
Volume 2
Chapter 14: The Steam Killing Demon released Oct 19 '16
Chapter 15: Innocent Villain released Oct 28 '16
Chapter 16: Princess Finisher-sama released Nov 9 '16
Chapter 17: She Looks Like the Princess and has the Same Brains as Her Too released Nov 18 '16
Chapter 18: Friend (Futon) released Nov 25 '16
Chapter 19: Badump! The Training Tournament Filled With Demons released Dec 4 '16
Chapter 20: A Flower's Life is Short released Dec 19 '16
Chapter 21: Why Can't Honey Be Produced From Nothing released Dec 26 '16
Chapter 22: Guardian of the Quiet Sleep released Jan 3 '17
Chapter 23: I'm Going to Visit You Tonight released Jan 17 '17
Chapter 24: My Laundry Path released Feb 1 '17
Chapter 25: On a Cradle Unto the Grave released Feb 20 '17
Chapter 26: Demon King Castle (Sleep) Paralysis Play released Mar 1 '17
Special 5: Volume 2 Extra released Feb 18 '18
Volume 3
Chapter 27: The Sloth Making Machine released Mar 15 '17
Chapter 28: Totally Fluffy Futon Taxi released Mar 28 '17
Chapter 29: Princess' Panties are Good Panties released Apr 12 '17
Chapter 30: I Can Upgrade the Window! released Apr 22 '17
Chapter 31: Although I got merged with a cat, isn't that okay...? released May 8 '17
Chapter 32: Because the Princess is a Naughty Girl released May 23 '17
Chapter 33: Stop Getting Serious in a Party Game! released Jun 4 '17
Chapter 34: Springy Princess released Jun 17 '17
Chapter 35: Sweet Dreams in the Outskirts of Demon King Castle released Jul 9 '17
Chapter 36: God's Move in Dream released Jul 28 '17
Chapter 37: A Perfectly Happy Prisoner released Aug 10 '17
Chapter 38: Demon King-sama's Sleep or Die released Aug 23 '17
Chapter 39: Keeping Secrets Isn't Good! released Sep 4 '17
Chapter 39.5: Volume 3 Extra released Aug 12 '18
Volume 4
Chapter 40: Chocolate is the Colour of Blood, the Colour of Love released Sep 17 '17
Chapter 41: Spine-chan Doesn't Sleep released Sep 19 '17
Chapter 42: Which Child Sleeps the Most? released Sep 24 '17
Chapter 43: Attack!! Forehead Devil Subspecies! released Oct 1 '17
Chapter 44: Create and Sing released Oct 6 '17
Chapter 45: The Girl Visiting Many Demon King Castles released Oct 12 '17
Chapter 46: Looks Like We Have a Master of All Trades released Oct 20 '17
Chapter 47: Taking Back the Princess (the Monster of Demon King Castle) released Oct 29 '17
Chapter 48: Badump! The Sorcery Tournament Filled with Demons! released Nov 7 '17
Chapter 49: I Want to Hit the Helpful Goods Jackpot released Nov 25 '17
Chapter 50: The Princess Dances Even If There Isn't A Meeting released Dec 15 '17
Chapter 51: Pollinated Princess released Jan 6 '18
Chapter 52: I Think That's A Sneaky Capture Method released Jan 14 '18
Chapter 53: Not Remembering A Something During A Deep Sleep released Jan 25 '18
Chapter 54: It's for the Sake of a Girl's Friendship released Jan 31 '18
Chapter 55: The Princess's Wonderful Pillow Store released Feb 17 '18
Chapter 56: The Flower Garden Lying Beyond Perseverance released Mar 3 '18
Chapter 57: Nooobody's At Fault! released Mar 21 '18
Chapter 58: The Princess's Sensitive Mouth released Apr 1 '18
Chapter 59: Super-Sized For Demon King Castle released Apr 13 '18 Very large size gap
Chapter 60: It's Against The Rules To Call Them An Adult Though released Apr 22 '18
Chapter 61: Sudden Change! Big Eggplant Earless Seal released May 6 '18
Chapter 62: Together with Suyaris Onee-chan released May 21 '18
Chapter 63: Don't Avert Your Eyes released May 22 '18
Chapter 64: The Black Full-Time Princess released Jun 4 '18
Chapter 65: Do You Really Believe I Would Correct My Behaviour After Seeing Somebody Else's? released Jun 11 '18
Chapter 66: Demon King Castle Prison Break released Jul 7 '18
Chapter 67: The Demons Turn Ghastly Pale, the Colour of Fatigue released Jul 27 '18
Chapter 68: Finger-Drawn Fireworks released Jul 28 '18
Chapter 69: Jiggly Isn't A Bad Flavour! released Aug 3 '18
Chapter 70: Night Rehearsal Practice (Wholesome) released Aug 4 '18
Chapter 71: Heartfelt Party Night released Aug 17 '18
Chapter 72: Muu Muu Land is the Country of Dreams released Aug 21 '18
Chapter 73: Outfit Exchange Treat released Aug 28 '18 Halloween
Chapter 74: Do Your Best Doppelgänger Succyun! released Sep 4 '18
Chapter 75: For the Sake of that Worthless Victory released Sep 4 '18
Chapter 76: How Many More Minutes Must I Stay Awake? released Oct 3 '18
Chapter 77: I Can Meet You In Your Dreams! released Oct 8 '18
Chapter 78: Princess Running released Oct 15 '18
Chapter 79: Samsara at the Church released Oct 19 '18
Chapter 80: Princess Mandragora released Oct 23 '18
Chapter 81: The Girl Travelling Between Castles Again released Nov 8 '18
Chapter 82: You Can't Possibly Hide, Right? released Nov 18 '18
Chapter 83: Don't Forget About Succyun released Nov 24 '18
Chapter 84: The Sleep Princess' Speech released Dec 15 '18
Chapter 85: Together With Spine-chan released Dec 25 '18
Chapter 86: Friend (Futon) (Stalker) released Dec 25 '18
Chapter 87: When It Comes To Movies, You Need Popcorn! released Dec 25 '18
Chapter 88: It Contains Handmade Chocolate released Dec 31 '18 Valentine's
Chapter 89: You Dug Into A Grave, Not A Kotatsu! released Jan 2 '19
Chapter 90: Don't "It'll Prick A Little" Me! released Jan 23 '19
Chapter 91: 1-on-1 in the Ward released Jan 25 '19
Chapter 92: Princess's Unimagined Poverty released Jan 26 '19
Chapter 93: Since It Feels Surprisingly Good The Moment You Support Someone released Feb 3 '19
Chapter 94: Lying is Despicable! released Feb 5 '19
Chapter 95: New Years Futon Material Trade Fair released Feb 10 '19
Chapter 96: If Somebody Gives You Their Name, You Have To Give Yours released Feb 12 '19
Chapter 97: Okay to Sleep, Okay to Fight released Feb 24 '19
Chapter 98: Journey to Getting Used to the Princess released Mar 2 '19 Hot spring
Chapter 99: Visiting the Nicest Places of Hell Springs Over and Over released Mar 5 '19 Hot spring
Chapter 100: Let's Show Some Skin, Whee! released Mar 13 '19 Hot spring
Chapter 101: Princess is Forever Dreaming released Mar 21 '19
Chapter 102: You'll Be Able To Sleep 100% During Fifth Period Math released Mar 27 '19
Chapter 103: The Secret World of Suyarrietty released Apr 4 '19
Chapter 104: Isn't it Alright to Lay Out the Album? released Apr 10 '19
Chapter 105: Pampered Bomb released Apr 30 '19
Chapter 106: Deadlines Turns Creatures Weird released May 5 '19