In the Edo period, a popular pastime was hyaku monogatari, or "a hundred stories". A crowd of
people would gather in a room where a hundred candles were burning inside andon lamps, which
had been covered in blue paper to create an eerie atmosphere. Then a hundred frightening supernatural
tales would be told, and after each one was finished, a candle would be put out. When the last story
was told and the room went dark, the demon called ao-andon was said to appear.¹

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1. source 1, source 1.