During this era, large mammals such as the now extinct Naumann elephant migrated into the Japanese islands, along with brown bears, giant deer, tigers, wolves and monkeys, several ice ages occurred, and intense and widespread volcanic activity produced thick layers of fertile soil in many locations.

Temperatures were about 9 deg C below present averages, creating subarctic conditions,[2] even in the vicinity of what would later become Tokyo Bay.

The site was discovered during construction on an expansion to the Shisui Parking Area on the Higashi-Kantō Expressway, and was excavated from 1999 to 2000.

In addition, there was obsidian which originated in what is now Nagano Prefecture or from Kōzushima, one of the Izu islands, as well as other stones typically found in variously locations in the northern Kantō region.

This indicates some form of long-distance trade and a maritime capability for the inhabitants of the Japanese archipelago even at that early time in prehistory.