Sleepy Princess in the Demon Castle

• Ja Kanji — 魔王城でおやすみ • Ja Romaji — Maōjō de Oyasumi • Genre — * Adventure • Fantasy comedy • Slice of life

• Type — manga • Author — Kagiji Kumanomata • Publisher — Shogakukan • Imprint — Shōnen Sunday Comics • Magazine — Weekly Shōnen Sunday • First — May 11, 2016 • Volumes — 32

• Type — TV series • Director — Mitsue Yamazaki • Writer — Yoshiko Nakamura • Music — Yukari Hashimoto • Studio — Doga Kobo • Licensee — Crunchyroll • Network — TV Tokyo, AT-X, BS TV Tokyo (TV network) • First — October 6, 2020 • Last — December 22, 2020 • Episodes — 12

• Portal — yes Sleepy Princess in the Demon Castle is a Japanese manga series written and illustrated by Kagiji Kumanomata. It has been serialized in Shogakukan's manga magazine Weekly Shōnen Sunday magazine since May 2016, with its chapters collected in 32 tankōbon volumes as of May 2026. An anime television series adaptation produced by Doga Kobo aired from October to December 2020.

The story follows Princess Syalis, a young princess who was kidnapped by the Demon King, and her quest to sleep well while imprisoned. Despite the Demon King's best attempts, the princess turns her kidnapping into a vacation; having grown tired with the stress of a royal life, she is indifferent to the situation.

• Princess Syalis: • Princess Syalis (full name: Aurora Sya Lis Goodereste) is a princess who was kidnapped by the demon king and causes chaos in the demon castle while trying to get a good night's sleep. She has been living at the demon king's castle for a year now due to her wishing to escape the stresses of royal life and making no attempt to escape. Before long, she begins accepting the demon castle as her new home. • Twilight the Demon King: • The leader of the demon race, who is also the one responsible for abducting Syalis. He is usually annoyed by her antics and sometimes get dragged into them. Despite being the Demon Lord, he is not all that intimidating or ruthless. • Akuma Shūdōshi: • A demon priest who has the power to bring those who were killed back to life. Most of the time, he had to revive Syalis after she accidentally kills herself or those that she killed for her own means. Like Twilight, he also sometimes gets dragged into Syalis's antics. He seems to have feelings for Syalis as he gets very jealous when anyone else demonstrates feelings for her. • Dawner the Hero: • Dawner is the hero who is entrusted by the Human Confederation of Goodereste with the task of saving Princess Syalis from the demon castle. Although Dawner and Princess Syalis are childhood friends and also engaged, she does not remember who he is. Whenever she mentions Dawner to the denizens of the demon castle, she calls him, "Daw-What's-His-Name". Due to Dawner being outgoing and friendly to Princess Syalis, yet being incredibly clumsy and prone to mistakes, he had always annoyed her, thus causing her to have nightmares when at one point he enters her dreams. He is also known for his poor sense of direction, which explains why Princess Syalis has been captive for a year, along with her unwillingness to escape. • Hari Toge Majiro: • One of Twilight's henchmen. He resembles a porcupine. • Frankenzombie: • One of Twilight's henchmen. He resembles Frankenstein's monster. • Minotaurosu: • One of Twilight's henchmen. • Yashiki Teshita Goburin: • One of Twilight's henchmen. • Reddo Shiberian-Kai: • Loyal retainer to the Demon Lord, in charge of enforcing rules. The princess drives him batty with her blatant disregard to the fact she is supposed to be a hostage. In fact, later in the series, he notes that the princess is costing them a fortune with all her misadventures, adding onto the woe everyone endures. • Obake Furoshiki: • He and his subordinates are the principal victims of Princess Syalis's antics, especially when she needs cloth to make things to get a good sleep. The death of the Ghost Shrouds by the Princess is a common joke in the series. • Obake Furoshiki • Monster Shroud's minions. • Poseidon: • A demon who has dominion over water. Because Poseidon never wears a shirt, the princess labels him a nudist. • Fire Venom Dragon: • A demon who has dominion over fire. He always wears a mask. • Neo Aruraune: • A gentle plant demon, who has motherly concern for the Princess. While willing to overlook all the deaths the Cleric is forced to undo, Neo Alraune became "miffed" upon realizing her tree trunk brother was killed by the Princess as part of one her usual ridiculous sleep plans. • Arājifu: • The spirit of a forbidden grimoire the princess freed by sheer dumb luck. Alazif tries encouraging Syalis to use his powers to defeat the demons and leave the castle; however, he is left severely disappointed with her due to her preoccupation with sleeping. • Scissors Sorcerer: • A demon with an arm made of scissors. Syalis gave him her crown to keep his arm together in exchange for his lost scissors; unfortunately, leading to her routine of killing the ghost shrouds. • Giaboruto: • A scientist demon. • Harpy: • A harpy who believes that the princess considers her a friend over a misunderstanding with Syalis wishing to nap on Harpy's feathers. • Hadesu: • Poseidon's older brother. Hades is always looking for chance to usurp the throne if Twilight messes up bad enough because of their mutual grudge. • Hypnos: • A sleep demon; he must sleep 20 hours a day or risk death. Hypnos was called to examine Syalis' nightmare at one point; revealing to the demons just how much the princess detests Dawner (the source of the nightmare). • Bussy/Cubey: • A succubus who looks eerily like the princess; only she has purple hair and gold eyes. Cubey wished to learn why the princess was so popular despite looking the same, but got sucked into being trained as her double. • Kaimīn no Joō: • Nemlis (full name: Aurora Nem Lis Goodereste) is the queen of Goodereste, a kingdom of humankind, and mother of Princess Syalis. • Teddy Demons: • Living teddy bears with wings. Syalis keeps one as a pet and bribes them into giving her the keys to her cell in exchange for being brushed. They soon develop a good relationship with her. • Morugen: • A muscular paladin who works in Goodereste's castle. • Evening Star: • A paladin who works in Goodereste's castle. He is only awake at night and falls asleep when it is daytime. • Keru Bero Ros: • Hades' subordinates. They are a trio of wolf demons. • Taiya Majin • A demon whose body is made of tires. Should his body be missing, he appears in gaseous form. • Aisu Gōremu: • A demon made of ice cubes. He is the leader of the ice demons. • Evil Tree Spirit: • Neo's unnamed older brother who is a demon that resembles a tree stump. Even when his body is cut up, he does not die so easily.

Written and illustrated by Kagiji Kumanomata, Sleepy Princess in the Demon Castle started in Shogakukan's manga magazine Weekly Shōnen Sunday on May 11, 2016. Shogakukan has collected its chapters into individual tankōbon volumes. The first volume was released on September 16, 2016. As of May 18, 2026, 32 volumes have been released. Viz Media announced in September 2017 that they had licensed the series in North America. The first volume was released on June 12, 2018. On May 9, 2023, Viz Media launched their Viz Manga digital manga service, with the series' chapters receiving simultaneous English publication in North America as they are released in Japan. An official fanbook of the series was released on October 16, 2020.

An anime television series adaptation was announced in Weekly Shōnen Sunday in September 2019. The series was animated by Doga Kobo and directed by Mitsue Yamazaki, with Yoshiko Nakamura handling series composition and Ai Kikuchi designing the characters. Yukari Hashimoto composed the series' music. The series ran for 12 episodes from October 6 to December 22, 2020, on TV Tokyo, AT-X, and BS TV Tokyo (TV channel). Inori Minase performed the opening theme Sleep! A Good Night's Sleep! Syalist Life, while Oresama (duo) performed the ending theme "Gimmme!". Funimation acquired the series and streamed it on its website in North America and the British Isles. On February 21, 2021, Funimation announced the series would receive an English dub, with the first episode premiering the next day. Following Sony's acquisition of Crunchyroll, the series was moved to Crunchyroll. In Southeast Asia and South Asia, the anime is licensed by Muse Communication, and released on Bilibili in Southeast Asia. The series premiered on Animax Asia on May 12, 2021.