This is a standing stone sundial feature of 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 “sundial” stone feature is located within the the Nonakado stone circle. The sundial features of the site are arranged in a manner that they point toward the sunset on the summer solstice. 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