Daizen-ji (大善寺), a temple of the Shingon sect (真言宗) in Kōshū, Yamanashi, enshrines a hibutsu (秘仏) image of Yakushi Nyōrai (薬師如来) that is revealed to the public once every five years. The temple traces its origins to the Nara period, traditionally attributed to the monk Gyōki (行基, 668–749), though the style of the principal image points to the early Heian period, and firm documentation begins with the reconstruction of the main hall in 971. It later served as the clan temple (氏寺 ujidera) of the Saigusa clan (三枝氏), a local gōzoku (豪族) that held power in the eastern Kōfu basin. During the Sengoku period, the temple came under the patronage of the Takeda clan. In 1582, Takeda Katsuyori (武田勝頼, 1546–1582), retreating after defeat at the Battle of Tenmokuzan, is said to have spent a night here, an episode later recorded by the nun Rikei (理慶尼) in her account of the clan’s fall, the Rikei-ni no Ki (理慶尼記).
