Kirk here with something for those of you who read Spanish. I searched but couldn’t find an equivalent article onf the Nippon.com site in English. Here’s a DeepL translation of part of the article:

“Hitoyoshi Castle was the residence of the Sagara clan, which ruled the area for about 700 years, from the late 12th century, when the Kamakura shogunate appointed Sagara Nagayori as lord of the land, until the Meiji Restoration (19th century). In the ruins of the residence of the Sagara’s main vassal, located in the fortress, a underground room containing a well was discovered, something unusual in Japan.”

https://www.nippon.com/es/guide-to-japan/castle00143093/