After walking down the mysterious alleyway, Endou finds himself in a mysterious city with luminous fish floating in the night sky. There, he finds Sumida, who tells him he's made his way to the riverbed city: KAWAZOKO. A fabled city of wonder his father had been searching all his life and the cause of his disappearance. Determined to discover more, Endou decides to stay, but Sumida gives him a stern warning to leave before the night of the Lantern Fair...
Japanese Title: 川底幻燈２ 幻燈市の夜
Have you read the prequel?