was a Japanese daimyo

Daimyo

is a generic term referring to the powerful territorial lords in pre-modern Japan who ruled most of the country from their vast, hereditary land holdings...

 of the Edo period, who served the Tokugawa clan

Tokugawa clan

The was a powerful daimyo family of Japan. They nominally descended from Emperor Seiwa and were a branch of the Minamoto clan by the Nitta clan. However, the early history of this clan remains a mystery.-History:...

. Masamitsu was the son of Hoshino Masanao, and after having lent his support to Tokugawa Ieyasu

Tokugawa Ieyasu

 was the founder and first shogun of the Tokugawa shogunate of Japan , which ruled from the Battle of Sekigahara  in 1600 until the Meiji Restoration in 1868. Ieyasu seized power in 1600, received appointment as shogun in 1603, abdicated from office in 1605, but...

 at the 1600 Battle of Sekigahara

Battle of Sekigahara

The , popularly known as the , was a decisive battle on October 21, 1600 which cleared the path to the Shogunate for Tokugawa Ieyasu...

, he was given the Takatō

Takato Domain

The was a Japanese feudal domain of the Edo period, located in southern Shinano Province. Its capital was at Takatō Castle, in what is today the city of Ina, Nagano Prefecture.-History:...

 fief in 1600.With his father's death the following year in Takatō, Masamitsu became the new head of the Hoshina family and served throughout the Osaka Campaigns of 1614 and 1615. Masamitsu was later privileged with the adoption of Tokugawa Hidetada

Tokugawa Hidetada

was the second shogun of the Tokugawa dynasty, who ruled from 1605 until his abdication in 1623. He was the third son of Tokugawa Ieyasu, the first shogun of the Tokugawa shogunate.-Early life :...

's fourth son Yukimatsu, the future Hoshina Masayuki.