Shinichirou Asano and Sakuya Shimazu, the 37th head of the monster-hunting Shimazu family, take a working vacation to one of the family's private islands with the rest of their circle. When companions start vanishing one by one while exploring the island's forest, the pair find themselves cut off and facing a supernatural threat alone. This single-episode OVA is a side story to the Isuca TV series rather than a continuation of its main plot.