The source material for the OVA "Tsuki ni Naku" is volume 11 of the manga, where the Hiizumi Life Counseling Office embarks on a trip to a hot spring resort. This excursion coincides with a fresh predicament for the local police in the form of a formidable youkai-hunter. The limited edition packages for manga volumes 14, 15, and 16 feature the inclusion of the OVA.