The sound of unusual noises and eerie tunes from an ancient crystal radio alerts Asuna Watase, prompting her to take a stroll to her clubhouse. Little does she know that this leisurely walk will instead thrust her into a terrifying adventure that leads her beyond the fabled realm and into a subterranean world. After being attacked by a monstrous entity, Asuna is saved by a mysterious individual and relentlessly pursued by a persistent enemy. As she becomes embroiled in an ancient mystery, she discovers an unexpected ally and is drawn towards a secret that could unlock the mysteries of existence itself.