It consists of several kuruwa terraces protected by stone walls and a deep dry moat.

[3] Kōkukuji Castle was originally built by the Imagawa clan to protect the eastern border of Suruga Province in the 15th century, but the exact date is unknown.

Yoshitada fell in battle in 1476 and as his son Imagawa Ujichika was still a minor, Ojika Norimitsu was appointed regent.

However, Norimitsu later refused to turn over power as agreed, so Hōjō Sōun and his henchmen had him killed in order for the succession to go to his nephew Imagawa Ujichika.

After the Battle of Sekigahara, Tokugawa Ieyasu assigned the castle to Amano Yasukage, one of his old retainers.