It is written in Koyo Gunkan, a record of military exploits of the Takeda Clan, that Takeda Harunobu (Shingen), at the young age of 20, led his retainers into battle against Murakami Yoshikiyo of Shinano in February 1540 following Yoshikiyo’s invasion and burning of Koarama with an army of more than 3,000, and scored a triumph. It is said that because Shingen enshrined a Jizo deity in prayer for victory before going into battle and subsequently won the battle, he built an esoteric Buddhist temple, which marks the beginning of Hossho-ji Temple. Recent studies, however, say that the battle had never actually existed.
It is also said that Shingen prayed for victory at this temple before the 1553 Battle of Kawanakajima.