In February 1540, Murakami Yoshikiyo of Shinano invaded Koarama with a troop of more than 3,000 soldiers and reduced the area to ashes. Takeda Harunobu (Shingen), at the young age of 20, led his retainers into battle and scored a victory at this site.
The erstwhile battlefield is dotted with stones associated with Shingen, such as the Goza-ishi (sitting stone), Tohmi-ishi (lookout stone), Kurakake-ishi (saddling stone), and a mound where severed ears are said to be buried. Excavation of the vicinity has yielded such artifacts as arrowheads, Buddha statues, swords, and the shell portion of helmets. A diminutive Suwa-jinja Shrine also stands among the ruins enshrining a small version of the sacred wooden pillar called Onbashira.
Nakayashiki, where Shingen based his troop, was the area on the east side of today’s Koarama Public Hall near Upper Bomichi Road, which was later said to have been cut open by Shingen for military purposes.