Lifespan: Tenshō 1 (1573) or Tenshō 5 (1575) to 2/26 of Keichō 9 (1604)
Rank: bushō, daimyō
Title: Junior Fifth Rank (Lower), Master of the Office of Palace Repairs
Lord: Toyotomi Hideyoshi → Toyotomi Hideyori → Tokugawa Ieyasu
Father: Kuwayama Kazushige
Siblings: Kazuharu, Kazunao
Children: Daughter (wife of an individual in the Tsumori clan), daughter (wife of Kuwayama Sadatoshi), Kazunao
Kuwayama Kazuharu served as a bushō and daimyō during the Azuchi-Momoyama and early Edo periods. In the Edo period, Kazuharu was the first head of the Yamato-Shinjō domain and the second head of the Kuwayama family in the domain. He held the titles of Junior Fifth Rank (Lower) and Master of the Office of Palace Repairs.
Kazuharu was born as the eldest son of Kuwayama Kazushige, making him the lineal grandson of Kuwayama Shigeharu. His childhood name of Kotōta was also used as his common name. During the Bunroku-Keichō Campaign on the Korean Peninsula, Kazuharu served with his uncle, Kuwayama Sadaharu, as commanders of naval forces, crossing the sea to Korea. Kazuharu contributed in battle but sustained injuries.
In 1596, his grandfather, Shigeharu, retired and entered the priesthood, adopting the name of Sōei. Meanwhile, Kazuharu’s father, Kazushige, had earlier died in 1582, so Kazuharu inherited the landholdings of the family in Wakayama in Kii Province.
In 1597, in the Kishū Uprising, Kazuharu helped break a siege of Tanabe Castle held by Asano Yukinaga prior to moving to Susaki and enabled suppression of the uprising.
In 1600, during the Battle of Sekigahara, Kazuharu remained in his territory. Initially, he supported the Western Army but the family was split between the Eastern and Western armies, so, later, Kazuharu and his grandfather, Shigeharu, joined the Eastern Army. Following orders, they attacked Horiuchi Ujiyoshi who was aligned with the Western Army. As a result, his rights to his landholdings were recognized after the war.
In 1601, his landholdings were moved to Fuse in the Katsuge District of Yamato where he became the first head of the Yamato-Shinjō domain. Later, he allocated 4,000 koku to his grandfather, Shigeharu while Kazuharu managed a fief of 16,000 koku.
On 2/26 (or 2/28) of Keichō 9 (1604), Kazuharu died in Fushimi in the environs of Kyōto. He was thirty or three-three years old and succeeded by his younger brother, Kuwayama Kazunao.