Based on a Japanese mystery novel series written by Tokuya Higashigawa and illustrated by Yuusuke Nakamura. Higashikawa penned the three-volume mystery novel under Shogakukan between September 2010 and December 2012, with illustrations by Yusuke Nakamura (Yojouhan Shinwa Taikei). A sequel novel, titled Shin Nazotoki wa Dinner no Ato de, began in March 2021. Shogakukan published the second volume on September 18, 2024.
The original novel inspired a manga adaptation by Aya Kawase that ran in Flowers Comics alpha magazine from April to November in 2011. Shogakukan released the second and final volume in August 2012.