Yamaoka Momosuke is tired of creating cryptic puzzles for children and has turned his attention to compiling a collection of sinister and scary stories, entitled Hyakumonogatari ("One Hundred Tales"). While researching ancient narratives for inspiration, he comes into contact with a mysterious trio calling themselves the Ongyou. Intent on revealing the truth concealed in these legends, these detectives are determined to hold those responsible accountable for their actions. With each meeting, Momosuke is compelled to expose uncomfortable truths while grappling with his own moral compass, all while witnessing inexplicable events.