【Different Mysteries for Each Bookstore】Limited Distribution at 4 Bookstore Chains! Original Mystery Cards Gifted to Purchasers of 'Mystery Detective Schloss'!
The first volume of 'Mystery Detective Schloss: Secret Detective Debut!', a children's book series from RIDDLER, led by Ryogo Matsumaru, was released on April 22, 2026. A campaign is now underway offering exclusive original mystery cards at 4 major bookstore chains, with different characters and mysteries available at each store, promoting a new reading experience that combines reading and mystery-solving.
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- 📰 Published: April 28, 2026 at 19:00
- 🔍 Collected: April 28, 2026 at 10:31
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The first volume of "Mystery Detective Schloss 1: Secret Detective Debut!", a children's book series from RIDDLER, a group of mystery creators led by Ryogo Matsumaru, was released on April 22, 2026. As an unprecedented new mystery children's book focusing on the themes of "reading," "solving," and "creating," it has garnered attention, and a bookstore-exclusive purchaser bonus campaign has now begun.
The participating bookstore chains are Kinokuniya Bookstore Group, Miraiya Bookstore & Asse, Kumazawa Bookstore Group, and Miyawaki Bookstore & Meirindo Bookstore (excluding some stores). Purchasers of "Mystery Detective Schloss" Volume 1 will receive an original mystery card available only at each specific bookstore (while supplies last).
A major feature of this bonus is that different characters and mysteries are prepared for each bookstore.
Kinokuniya Bookstore Group features the protagonist Hayato, Miraiya Bookstore & Asse features the heroine Chinatsu, Kumazawa Bookstore Group features Schloss member Kazuma, and Miyawaki Bookstore & Meirindo Bookstore (excluding some stores) features Schloss member Yuina. Each character card contains an original mystery that can only be challenged there. Furthermore, on the back, where the answers and explanations are provided, Phantom Thief R, the leader of the Mystery Detective Schloss, appears.
Moreover, the problems and answers are themed around "books" and "each bookstore," in addition to the world of the work. Readers who feel that the 9 questions included in the book are not enough are encouraged to collect all 4 types and challenge all the mysteries.
"Mystery Detective Schloss" allows readers not only to read the story but also to actively solve mysteries and even create their own. This bookstore campaign is likely to further increase the number of readers who experience the joy of mystery solving.
### Synopsis
"If you don't want your secrets revealed... become a phantom thief."
Recently, an unidentified phantom thief group "Schloss" has been stirring up the school by setting up mysteries. Chinatsu, a girl who admires famous detectives, harbored a strong rivalry against them. Hayato (the protagonist), a boy acting as Chinatsu's "assistant," unexpectedly becomes a member of the phantom thief group "Schloss" one day.
If Chinatsu finds out, she will surely hate him—.
Hayato finds himself creating mysteries as a "phantom thief" while holding a secret that must never be revealed...
A new series where secrets, lies, and flashes of inspiration intersect: "School × Phantom Thief × Mystery Solving," opens here!
### Comment from Author Ruyosanto!!
"I started writing this story with the hope that even a few more children would want to 'create mysteries'." I've also prepared a special surprise at the end. Please enjoy the story with paper and pencil in hand!
### Author Profile
Author: Ruyosanto
Born in Ishikawa Prefecture in 1996. Graduated from and completed graduate studies at the University of Tokyo. Belongs to RIDDLER Inc., a group of mystery creators. Books include "Pleiades in the Summer Sky" (Shogakukan), "Aim for! Nazotore Koshien" and "Mystery Ink Battle Survival" (both Fusosha). Recipient of the 16th Sogen SF Short Story Award.
Planning: RIDDLER
A group of mystery creators led by Ryogo Matsumaru. With the motto "Create the best 'aha!' experiences and make everyone love thinking," they are widely active in television, books, events, regional revitalization, and educational projects.
Illustrator: Ozido
Born in 1999. Illustrator living in Okinawa Prefecture. Mainly creates animations and illustrations with a pop art style.
### Bibliographic Information
Title: "Mystery Detective Schloss 1: Secret Detective Debut!"
Author: Ruyosanto
Release Date: April 22, 2026 (Wednesday)
Format: Shirokuban
Pages: 224P
Price: 1,320 yen
Publisher: Futabasha
https://www.futabasha.co.jp/book/97845753206880000000
The participating bookstore chains are Kinokuniya Bookstore Group, Miraiya Bookstore & Asse, Kumazawa Bookstore Group, and Miyawaki Bookstore & Meirindo Bookstore (excluding some stores). Purchasers of "Mystery Detective Schloss" Volume 1 will receive an original mystery card available only at each specific bookstore (while supplies last).
A major feature of this bonus is that different characters and mysteries are prepared for each bookstore.
Kinokuniya Bookstore Group features the protagonist Hayato, Miraiya Bookstore & Asse features the heroine Chinatsu, Kumazawa Bookstore Group features Schloss member Kazuma, and Miyawaki Bookstore & Meirindo Bookstore (excluding some stores) features Schloss member Yuina. Each character card contains an original mystery that can only be challenged there. Furthermore, on the back, where the answers and explanations are provided, Phantom Thief R, the leader of the Mystery Detective Schloss, appears.
Moreover, the problems and answers are themed around "books" and "each bookstore," in addition to the world of the work. Readers who feel that the 9 questions included in the book are not enough are encouraged to collect all 4 types and challenge all the mysteries.
"Mystery Detective Schloss" allows readers not only to read the story but also to actively solve mysteries and even create their own. This bookstore campaign is likely to further increase the number of readers who experience the joy of mystery solving.
### Synopsis
"If you don't want your secrets revealed... become a phantom thief."
Recently, an unidentified phantom thief group "Schloss" has been stirring up the school by setting up mysteries. Chinatsu, a girl who admires famous detectives, harbored a strong rivalry against them. Hayato (the protagonist), a boy acting as Chinatsu's "assistant," unexpectedly becomes a member of the phantom thief group "Schloss" one day.
If Chinatsu finds out, she will surely hate him—.
Hayato finds himself creating mysteries as a "phantom thief" while holding a secret that must never be revealed...
A new series where secrets, lies, and flashes of inspiration intersect: "School × Phantom Thief × Mystery Solving," opens here!
### Comment from Author Ruyosanto!!
"I started writing this story with the hope that even a few more children would want to 'create mysteries'." I've also prepared a special surprise at the end. Please enjoy the story with paper and pencil in hand!
### Author Profile
Author: Ruyosanto
Born in Ishikawa Prefecture in 1996. Graduated from and completed graduate studies at the University of Tokyo. Belongs to RIDDLER Inc., a group of mystery creators. Books include "Pleiades in the Summer Sky" (Shogakukan), "Aim for! Nazotore Koshien" and "Mystery Ink Battle Survival" (both Fusosha). Recipient of the 16th Sogen SF Short Story Award.
Planning: RIDDLER
A group of mystery creators led by Ryogo Matsumaru. With the motto "Create the best 'aha!' experiences and make everyone love thinking," they are widely active in television, books, events, regional revitalization, and educational projects.
Illustrator: Ozido
Born in 1999. Illustrator living in Okinawa Prefecture. Mainly creates animations and illustrations with a pop art style.
### Bibliographic Information
Title: "Mystery Detective Schloss 1: Secret Detective Debut!"
Author: Ruyosanto
Release Date: April 22, 2026 (Wednesday)
Format: Shirokuban
Pages: 224P
Price: 1,320 yen
Publisher: Futabasha
https://www.futabasha.co.jp/book/97845753206880000000