He was the 7th son of Nanbu Toshinao, the 1st daimyō of Morioka Domain, and was originally named Nakasato Naiyoshi (中里直好).

In 1664, his elder brother, Nanbu Shigenao (the 2nd daimyō of Morioka Domain) died while under house arrest in Edo without an heir.

Naomasa was noted as a scholar; however a series of crop failures due to inclement weather occurred in the Enpō era (1673-1680) caused economic problems for the domain, which was compounded by the expenses needed for sankin-kōtai, which was imposed on the domain by the Tokugawa shogunate in recognition of its “independent” status.

[2] As of 1695, the first survey was made of Hachinohe Domain, which recorded a population of 58,507[2] He died in 1699 at age 39.

Nanbu Michinobu (南部通信, March 29, 1673 - October 9, 1716) was the 3rd daimyō of Hachinohe Domain.

He was a multitalented person, noted for his knowledge of literature, horsemanship, the Japanese tea ceremony, waka poetry, and kemari.

Nanbu Hironobu (南部広信, April 16, 1704 - June 14, 1741) was the 4th daimyō of Hachinohe Domain.

During his tenure, a complete survey of the domain's lands was undertaken, and the Hachinohe Sansha Matsuri festival began;[2] however, the domain continued to be plagued by frequent crop failures due to inclement weather.

Per a census in 1732, the domain had 56,401 inhabitants [2] He died at the age of 33, and his grave is at the temple of Konchi-in in Minato, Tokyo.

Nanbu Nobuoki (南部信興, October 27, 1725 - September 29, 1773) was the 5th daimyō of Hachinohe Domain.

Nanbu Nobufusa (南部信房, August 1, 1765 - June 7, 1835) was the 7th daimyō of Hachinohe Domain.

He was the eldest son of Nanbu Nobuyori, and was presented in formal audience to Shōgun Tokugawa Ieharu in November 1780.

During his tenure, the domain suffered severely from the Great Tenmei famine of 1783 during which 30,000 of the 65,000 inhabitants died [2] and he was forced to borrow large sums of money from local merchants.

Unable to repay these debts, Naoyori was forced to raise a number of the merchants to samurai status.

The measures were initially successful, albeit highly unpopular, and when the Tenpō famine of 1834 struck, there was a widespread uprising.

During the Bakumatsu period, he sided with the Tokugawa shogunate against the Satchō Alliance, and during the Boshin War, took his domain into the Ōuetsu Reppan Dōmei.