This is a stone feature at the Oyu Stone Circle site in Akita, Japan. The Oyu site consists of two stone circles, the larger Manza stone circle is approximately 52 meters in diameter, while the smaller Nonakado stone circle is approximately 44 meters in diameter. This feature is located within the the Manza stone circle. The Oyu site dates to the Late Jomon period (apx 4,000 – 3,500 BP) and is one of several Jomon period sites in the Tohoku and Hokkaido regions designated as UNESCO World Heritage sites in 2021.
More information on the site can be found here: https://jomon-japan.jp/en/learn/jomon-sites/oyu