Naraku no Shiro Portable Ichiyanagi Nagomu, Nidome no Junan

Following the Amagoushi no Yakata case, detective Nagomu Ichiyanagi accepts an invitation from his friend Hiori to visit a medieval castle in rural Europe — accessible only by rope bridge across a deep valley. Over dinner, the owner recounts the estate's history: an ancestor who practiced black magic and sacrifice rituals, eventually summoning a demon that possessed a young victim, who was then sealed inside the castle. The victim's mother entered to find him and also disappeared. The castle's lights go out. Everyone can feel something in the air.