Hieyama Chikaoki served as a bushō during the Sengoku and Azuchi-Momoyama periods. He was a retainer of the Chōsokabe clan and served as the lord of Hieyama Castle in Tosa Province. Chikaoki was a cousin of Chōsokabe Motochika, the sengoku daimyō of Tosa and twenty-first head of the Chōsokabe clan.
Chikaoki was born as the son of Chōsokabe Kuniyasu, the younger brother of Chōsokabe Kunichika. Chikaoki became the lord of Hieyama Castle in Tosa and adopted the name of the Hieyama clan.
During the Conquest of Shikoku by the Toyotomi army, Chikaoki defended Awa-Iwakura Castle. The death of Chōsokabe Nobuchika (the eldest son of Motochika) at the Battle of Hetsugigawa led to a power-struggle in the Chōsokabe clan with respect to the designated successor to Motochika. Chikaoki invited the fury of Motochika, and, on 10/4 of Tenshō 16 (1588) (or the end of the ninth month), he was compelled to commit seppuku.
At this time, Kira Chikazane was also compelled to commit seppuku, while Chikaoki’s wife and two children attempted to flee but were killed either on the road or at the Zenshō Castle. In total, among Chikaoki, his wife and children, and the abbot of the temple, a total of seven individuals were killed or took their own lives. Their spirits referred to as the Seven of Misaki gave rise to a legend known as the Hieyama Seven of Misaki.