At the Battle of Nagashino in 1575, Suganuma Sadatada had served with Takeda Katsuyori during the siege of Nagashino Castle, but suffered greatly during the actual battle itself. Katsuyori himself managed to flee from the battlefield and accompanied by Sadatada, sought refuge at Sadatada’s Damine Castle. Upon their arrival, they discovered that Sadatada’s uncle, Suganuma Sadanao, supported by clan vassal Imaizumi Dozen, had defected to the Oda clan, and shut the gates on Sadatada and Katsuyori. They were then forced to escape to Busetsu Castle, about 20 kilometers away.

In revenge for this act of treason, Sadatada faked his own death, thus relaxing security at the castle. Early one morning, Sadatada and an army of loyal followers attacked Damine Castle, capturing the fortress along with his uncle, Sadanao and Imaizumi Dozen. Both were executed in a public area near the castle along with 100 other traitors. Less than six years later, the Takeda clan was ruined. Fearing the growing strength of the Tokugawa, Sadatada left Damine Castle and retreated to Ina in modern-day southern Nagano Prefecture. Damine was soon claimed by the Tokugawa, who established another branch of the Suganuma clan and trusted vassals, as castellan.

Located on the Ina Kaido Highway, an important route connecting Ina, Nagashino, and Iwamura in what was then the country of Mino (present-day Gifu Prefecture); the then Koromo Province (present-day Toyota City) in Aichi Prefecture; and Hamamatsu in Shizuoka Prefecture, Damine Castle covers a square-shaped area of about 200 meters on each side. Dry moats and earthen embankments surrounded the western-facing front of the castle, with its many terraced kuruwa, or precincts. The uppermost precinct—the hommaru—was oval in shape and contained the lord’s residence and working area, a watchtower, retainer’s quarters, guard houses, possibly stables, and kitchen facilities. The eastern-facing rear of the castle was not so heavily fortified, being protected by the naturally steep cliffs along the Toyo River far below.

Although the castle was abandoned during the Edo period, the castle ruins remained in relatively untouched condition, allowing for research and for the reconstruction of numerous features, including the Goten Palace, the watchtower, gates, and fencing to create a fine reconstruction of a Warring States-period castle.