Yakumo Koizumi, who changed his name to Lafcadio Hearn and became a naturalized Japanese citizen, met Saburo Koga, a government official, in a village he visited with his disciple Yaichi Aizu , and witnessed the main exorcism of the village's secret festival, Natsukoshi, and was transported to the ``Yūkai''. I got into it. Since then, Yakumo has been involved in strange incidents.