Onigashima Cave 鬼ヶ島大洞窟
400 metres of cave dug by hand, opened in 1931 as the lair of the oni of legend.
A cave on Mount Washigamine, in the upper part of the island of Megijima (女木島), also known as Onigashima (‘the island of demons’) for its link with the legend of Momotarō. Reported in the early twentieth century by the local historian Hashimoto Sentarō, it was opened to the public as a tourist attraction in 1931.
Kagawa
Great Onigashima Cave
https://theanimetrip.com/luoghi/grotta-di-onigashima-megijima