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Completely! Halloween (なりきれ! 逆ハロウィン) is the thirty-seventh chapter of the Overlord: The Undead Oh! series.


Ainz Ooal Gown is greeted by the sensual appearance of Albedo clad in only an apron asking if he wants a "trick or teat". Ainz ignores the gag much to Albedo's shock as he resumes working to talk about Momon's latest activities. The lack of reaction infuriates the Overseer Guardian. Ainz remembering her quote on "trick or treat" asks if she was doing it for Halloween, but Albedo is not familiar with the term. She wonders if perhaps she did something wrong when she said it, but that is not the case as Ainz explains that Halloween is a festival. The Overlord tries to think of how to explain the holiday, but even his knowledge is limited knowing that it a holiday that originated from Europe and has something to do with pumpkin harvests. He does know that spirits and monsters have a heavy influence, though for Japan there seems to be some relation to the Obon Festival.

Ainz comes up with an answer that it is a festival for costumes and sweets. Albedo wonders if the outfit that she wore counted as being in the Halloween spirit as she was dressed as a "house wife." The Overlord provides her with more information telling her that Halloween is a celebration created by humans who wear costumes of beings that they fear, such as ghosts, devils, vampires, zombies, and skeletons. Taking that into account every day in the Great Tomb of Nazarick is Halloween as its full of monsters just like what he described. Anyway, people wear costumes and come together and party which Albedo think is fun. Ainz suggests that they host one themselves if they want to experience a Halloween. Albedo is happy at the suggestion, though wonders what kind of costume they should wear. As there are not any beings the denizens of the tomb feel afraid of save for Ainz. Seeing that bumping into multiple people that look like him would be a problem, Ainz reiterates that the costumes should be unique. They should try to be as creative as possible and tells her that the holiday according to his friends was started because humans wished to blend in with monsters to avoid being caught. Later in the Throne Room, Albedo announces the upcoming Halloween Festival, calling it an audition to practice infiltrating human society.

On the day of the festival, Ainz wearing his Mask of Envy is greeted by the "trick or treat" calls of Aura Bella Fiora and Mare Bello Fiore dressed as humans, by hiding their ears, and in mountain folk clothes. The magic caster is surprised when they offer him candy, as they are doing the reverse. They guide Ainz to the party venue, where it seems everyone is dressed like a human. A few however cannot successfully disguise themselves like Cocytus. However, he and CZ2128 Delta teamed up, with the automaton pretending to be an adventurer while Cocytus is her golem servant in order to blend in human society. Ainz is impressed with the idea the two had come up with. Shalltear Bloodfallen calls her master out showing her set costume, being a patient on a medical bed with a Vampire Bride dressed as a nurse. The Floor Guardian is rather proud of her costume, she even included Yuri Alpha to dress as a doctor, but her ego is burst when Ainz tells her the outfits they are wearing don't correspond with the medical attire outside of Nazarick.

Ainz then encounters Demiurge, recognizing his voice, who is dressed in a costume that masks his face and covers his entire body. Mare seeing Demiurge's mask and gown wonders if he is a beekeeper, but Ainz corrects him stating he is a plague doctor, a medieval doctor during the Black Death. After seeing Demiurge, Ainz cannot help but compare the costume to being similar to his friend Ulbert Alain Odle. Aura comments that there aren't any infectious diseases existing outside in the New World, thus he won't be able to blend in well in human society even in that get-up. Demiurge doesn't think that it's much of an issue as they can always introduce the Black Death. Thankfully, he is just joking much to Ainz's relief. The Overlord soon hears that Albedo is using this costume party to select additional personnel for the human infiltration team much to his surprise. Both Aura and Shalltear try to suggest to Ainz that they are best suited for infiltrating human society, and as they fight Ainz cannot help but feel that this is like job hunting.

He wonders where Albedo is, and receives his answer when she shows up dressed in her Hermes Trismegistus pushing a baby carriage, hailing herself as an adamantite adventurer with her "child". Shalltear sees what Albedo is trying to do, and accuses her of seeking to replace Narberal Gamma as Momon's adventurer partner. Albedo admits to this stating that she boasts the highest defense and thus is suitable to protect Ainz. As for the baby in the carriage, who is revealed to be Victim wearing a onesie, Albedo included him believing it to be a perfect addition for her master's protection.

Ainz, now forced to make a choice whose costume is the best among the party-goer ultimately selects Victim as he is perfectly disguised as a baby. Ainz excuses himself to return Victim back to the 8th Floor. Albedo shocked that she still wasn't selected by Ainz, falls into her delusions of her and Ainz having a child together. Later on, Ainz and Victim are seen alone together in the former's office. Victim is still wearing his costume, having grown fond of dressing like a toddler.

Character Appearances[]

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Chapter Notes[]

  • This chapter first appears in the Monthly Comp Ace May 2020 Issue.


Overlord: The Undead Oh! Chapters
Volume 1
1 2 3 4 5 6
Volume 2
7 8 9 10 11.1 11.2 12
Volume 3
13 14 15.1 15.2 16 17 18
Volume 4
19 20.1 20.2 21 22 23 24
Volume 5
25 26 27.1 27.2 28 29 30
Volume 6
31 32.1 32.2 33 34 35 36 Bonus
Volume 7
37 38 39 40 41.1 41.2 42
Volume 8
43 44 45 46 47 48
Not in a Volume
49 50 51.1 51.2 52