Lifespan: Tenbun 1 (1532) to 2/9 of Genna 2 (1616)
Other Names: Mitsu-jirō, Jibu-tayū
Rank: sengoku daimyō
Bakufu: Edo – hatamoto
Lord: Tokugawa Ieyasu
Father: Iwamatsu Ujizumi
Children: Kiyozumi, Toyozumi, Wakiya Sumitoshi, Wakiya 宗度, Wakiya Shigemasa, Higashi-no-tsubone (wife of Chiba Kunitane)
Iwamatsu Morizumi served as a sengoku daimyō of Kōzuke Province during the Sengoku and Azuchi-Momoyama periods and as a hatamoto, or direct retainer of the bakufu, during the early Edo period. Morizumi served as the fourteenth head of the Nitta-Iwamatsu clan.
The Nitta-Iwamatsu originated from the Iwamatsu township in the Nitta manor of Kōzuke in the early thirteenth century.
In 1532, Morizumi was born as the eldest son and lineal heir of Iwamatsu Ujizumi. His father, Ujizumi, was subjected to the despotic behavior of the head of the chief retainers, Yokose Narishige (later, Yura Narishige) and, in 1548, took his own life.
As a result, Morizumi inherited the headship of the clan, but Morizumi himself was also the target of Narishige’s high-handedness, and, in the end, lost his base at Nitta-Kanayama Castle. At this point, the Iwamatsu were extinguished as a daimyō family.
In 1590, after Tokugawa Ieyasu entered the Kantō, he sent a letter of congratulations. After establishment of the Edo bakufu, in 1611, Morizumi and his lineal heir, Iwamatsu Toyozumi, were engaged in service by Ieyasu but, when showing the genealogy of the Nitta clan who were his ancestors, he made a verbal slip so was sent home empty-handed. This outcome may have been in relation to the assumption by Ieyasu of being a descendant of the Nitta clan such that Morizumi stated that his family was the main branch, and even if the Tokugawa family were descendants, they were an offshoot of an illegitimate branch. This, however, cannot be authenticated from primary sources.
Thereafter, he became a hatamoto, or direct retainer of the bakufu, with a fief of 20 koku in the quarters of the Kannō Temple in the village of Ichinoi in the Nitta District of Kōzuke. Later, his residence was moved by the official managing this land, Kurokawa Masahide, to Serada. In 1616, Morizumi died at the age of eighty-five.
He was succeeded by his eldest son and heir, Iwamatsu Toyozumi.