The ruins of Onnemoto Chashi are located near the tip of the Nemuro Peninsula in Nemuro City, Hokkaido, and are the remains of a fort believed to have been built by the Ainu people between the 16th and 18th centuries. "Chashi" means "fenced enclosure" in the Ainu language, and was used for various purposes, such as a lookout post for the village and a place for holding ceremonies. 32 ruins of chashi have been confirmed on the Nemuro Peninsula, 24 of which have been designated as national historic sites as the "Nemuro Peninsula Chashi Ruins Group." Among them, Onnemoto Chashi is a representative site that is well preserved and maintained for viewing.

The charm of this ruins of chashi is its unique topography, with artificial embankments and trenches remaining. The small hill at the tip of the cape is said to look like an "offering rice cake," and its topography was created by skillfully utilizing the natural topography, evoking the wisdom and lifestyle of the Ainu people. The surrounding native plants and the scenery exposed to the harsh sea breeze tell the story of the harshness of the easternmost part of Hokkaido and the history of the people who lived there.

The Wonnemoto Castle ruins have historical value as a fortress and ceremonial site rather than a castle, and have been selected as one of the 100 Great Castles of Japan, making them an important destination for history lovers.

[Useful points of concern]
The Wonnemoto Castle ruins are only man-made embankments and trenches, and there are no buildings or flashy appearances, so they are a recommended spot for those who want to visit while imagining what life was like at the time.