Phantom Solitaire's Art of Disguising Oneself as a Supernatural Being

 refers to a Dead Mount Death Play spin-off gaiden novel about Phantom Solitaire and its manga adaptation of the same name. It tells the tale of Solitaire's criminal debut while intercutting it with scenes from the manga's present-day main storyline. Both the gaiden novel and manga are serialized in the Young Yangan app Manga UP!; the former began serialization on May 08, 2023, and the latter on November 2025 of the same year.

Novel Serialization
The spin-off serialization was announced in early Spring 2023. To promote the story, Young Gangan included its first installment with Dead Mount Death Play ' s ninety-ninth chapter in the magazine's tenth volume; Yen Press included a translation of that installment in the English release of Chapter 100. Ryohgo Narita explained on April 21 that the spin-off would use material that he had to set aside while writing the main story. "Before I knew it," he wrote, "All the parts that I had eliminated were connected!"

Gaiden Novel
On November 25, 2023, the story's first ten installments were collected in a gaiden novel published by Square Enix. The volume features story and character illustrations by Shinta Fujimoto.

The chapter list below includes the original Japanese titles and approximate English translations.

Cast
At least a few familiar faces from the main manga besides Solitaire's appear in the spin-off, those being Tsubaki Iwanome, Kōzaburō Arase, Kochou Eightport, and Gioacchino Soldati. As for the rest of the spin-off's cast, some characters are those who previously had only been referenced by name in the main manga, and others are brand new to the series.

The wiki has yet to confirm all character appearances in the spin-off. Listed below, however, are the six characters who have character illustration sheets at the end of the first gaiden novel volume. They are listed below.

On names: The Poisoner, Riddle Riddle, Komura Korone, and Himura (family name only) are all official English translations. The given names of Himura and the other two characters can be readily surmised (Emihiko, Charlot, Misa), but Charlot(te) and Misa's family names are trickier.


 * Spin-off characters who have been previously alluded to in the manga include:


 * Emihiko Himura (火村 笑彦 Himura Emihiko): A cold-eyed slender man who does not smile despite his name (Emihiko: smiling/laughing man). Senior of Komura and Eightport. (In the DMDP manga, the Weekly Dry Chief Editor makes reference to 'Himura...[a] veteran reporter' at least twice.)
 * The Poisoner (誕毒犯): An elderly man who frequents Youtoukorou's half-basement floor. Lisa Kuraki calls him 'sensei.' He wears a gas mask just like Kazami Asaura. (The Poisoner is one of the troublemakers mentioned early on in the DMDP manga. Kazami, who is said to be the Poisoner's apprentice, has at least two manga appearances.)
 * Riddle Riddle (リドルリドル): A Shinjuku troublemaker who always asks unintelligible questions. His masks, which are neither human nor animal, are adhered to his face and are muted in color. (Riddle Riddle was first mentioned in the DMDP manga at the same time the Poisoner was first mentioned.)


 * New characters include:


 * Korone Komura (狐村 コロネ Komura Korone): A Weekly Dry rogue reporter who is technically the senior of the newcomer Kochou, though they were/are both considered part of the "Weekly Dry Suicide Squad"'s rookie roster. She accidentally got caught up in Solitaire's debut crime three years ago and "became the exclusive 'Solitaire keeper'" as a result.
 * シャルロ ー・フィストランス (poss. TL: Charlot Fistrance): The 25-year-old daughter of the Fistrance Group's president. She came to Japan from overseas as the [Group's?] Japan Bureau Chief.
 * 黒屋敷 ミサ (poss. TL: Kuroyashiki Misa): A runaway whom Sorimura kidnapped after talking to her. She appears to be an ordinary woman, but she has an incredible grip.