《很久很久以前，在某个地方有一具尸体》
《很久很久以前，在某个地方有一具尸体》 is the 青柳碧人 book at the center of 99.很久很久以前，妖怪也推理啊…. The 蜜獾吃书 episode presents it as a Japanese folk-tale mystery collection: old stories supply the cast, magic, taboos, and impossible premises, while the author uses those premises to build 本格推理 mechanisms.
The episode focuses most on two stories. The 一寸法师 case turns small body size, an ogre’s belly, a festival taboo, and a magic mallet into alibi and semi-locked-room machinery. The 猿蟹合战 case turns a revenge tale into a logic-flow puzzle where role names, shapeshifting, mistaken identity, and exchange murder have to be reconstructed.
The source also briefly maps other stories in the series: 花开爷爷 becomes a death mystery, 鹤的报恩 uses narrative trickery, 浦岛太郎 uses a time-stopping shell for impossible crime, 桃太郎 turns鬼岛 into a closed-circle setup, and饭团咕噜噜 adds repeated-death investigation. Together these examples make the book a compact case of 民间故事推理改写.