Ryoko's Case Files

is a series of light novels written by by Yoshiki Tanaka and illustrated by Narumi Kakinouchi that started in October 15, 1996 and complete on December 20, 2018 while producing 11 volumes published by Kodansha. A manga adaptation by the same team was serialized in Kodansha's seinen magazine Magazine Z from March 1, 2004 to March 1, 2009 and produced 11 tankōbon volumes which was ended by the magazine closing. The manga was transferred to Monthly Afternoon starting on March 25, 2009 and it was renamed and resulted in 2 tankōbon volumes. The series finished on November 25, 2009. A third series, titled, started on January 25, 2010 and ran to September 25, 2010 resulting in 2 tankōbon volumes. A fourth series, titled was serialized from August 25, 2012 to November 24, 2012 resulting in 1 tankōbon volume. A fifth series, titled was serialized in  December 25, 2012 to September 25, 2013 resulting in 2 tankōbon volumes.

A spin-off manga was also created by Yoshiki Tanaka and Narumi Kakinouchi, titled SP Yakushiji Ryōko no Kaiki Jikenbo Tanpenshū (SP 薬師寺涼子の怪奇事件簿 短編集), compiled in three volumes, released from June 17, 2008 to November 22, 2011.

An anime TV series adaptation aired from July 6, 2008 to September 28, 2008 for 13 episodes. Two drama CDs had also been released prior to the anime adaptation with different voice actors from the CD and the TV version.

As the light novels, manga and the anime have different plots and paranormal events/creatures, their central plots are most of the time different from each other.

Plot
Based on a series of light novels written by Tanaka Yoshiki and illustrated by Kakinouchi Narumi.

The story revolves around Ryouko Yakushiji, a 27-year-old multilingual investigator that graduated from Tokyo University's elite Department of Law, and the bizarre cases she faces while working for the Tokyo Metropolitan Police. Yakushiji not only has to deal with supernatural beings in her line of work, but also her rival Yukiko Muromachi, another equally talented and beautiful police investigator.