In 1519, Takeda Nobutora, Takeda Shingen’s father and warlord in the Kai Province, built a place of residence for the Takeda Clan in Tsutsujigasaki. The following year, he built Yogaisan-jo Castle atop Mount Maruyama, which rose 770 meters above sea level behind the residence as a refuge for the clan in emergency situations.
In 1521 a year after the mountain castle was completed, Suruga forces invaded the Kofu Basin in droves. Nobutora’s wife Lady Oi, who was pregnant at the time, is said to have fled to the castle and gave birth to Shingen there (there is also a legend that she gave birth to Shingen at Sekisui-ji Temple).
For 62 years until Nobutora’s grandson Katsuyori relocated to Shimpu-jo Castle in Nirasaki, Yogaisan Castle served as the stronghold of the Takeda Clan’s territorial control along with the Tsutsujigasaki Residence, through three generations headed by Nobutora, Shingen, and Katsuyori. Today, the castle is a nationally designated Historic Site. In addition to characteristic buildings that are relatively well preserved and retain a sense of what life was like back in those times, remains of the castle include a well that still delivers water and is called “Suwa Water” because it was realized by praying to Suwa Myojin, in addition to a stone statue of Takeda Fudoson and a stone monument with an inscription by Togo Heihachiro denoting the birthplace of Takeda Shingen.