The anime features an original story based on volumes 1, 2, 5, and 6 of the original work.
Based on a mystery novel series written by Manabu Kaminaga, published by Nihon Bungeisha with illustrations by Katoh Akatsuki and later published by Kadokawa Bunko with cover illustrations by Yasushi Suzuki. The book has been adapted into two manga series, this anime, a live-action drama series and a stage play. The series ended publication in 2020 with a total of twelve volumes.