Chablo, Land of Primitive Men

(from ebookjapan):

In April 1926, the young Dr. Asahina, who was taking aerial photographs deep in the Greater Amazon region of South America, photographed a man-made fence on a cliff.

Earlier, primitive people were discovered in a village near the entrance to the unexplored Chablo. An investigation team including Dr. Asahina is formed, and Kazumasa heads for the unexplored Chablo, but what does he encounter there?

A jidaigekiga "Nozarashi Narugen" and 4 other stories are included in this collection.