Lifespan: 15xx to 8/25 of Keichō 8 (1603)
Other Names: Jirō-shirō, Jirōbei-no-jō
Lord: Shimazu Yoshihisa → Shimazu Yoshihiro
Father: Niiro Tadataka
Mother: Daughter of Uehara Naotsune
Wife: Daughter of Kimotsuki Kanemori
Children: Daughter (wife of Niiro Tadakiyo), daughter (wife of Katsura Tadayasu)
Adopted Children: Tadakiyo (lineal heir of Niiro Tadamasu)
Niiro Tadamitsu served as a bushi during the Azuchi-Momoyama and early Edo periods. He was a retainer of the Shimazu clan.
Tadamitsu was born as the lineal heir of Niiro Tadataka.
Prior to the conduct of Tadamitsu’s coming-of-age ceremony, his father, Tadataka, died in 1583 during an assault against Fukae Castle (which was aligned with the Ryūzōji clan) in Hizen Province.
On 8/22 of Tenshō 14 (1586), Tadamitsu was crowned by Shimazu Yoshihisa at his coming-of-age ceremony held in Yatsushiro in Higo Province. He received items to be worn from the waist and the same common name as his father, Jirō-shirō.
In 1587, as an outcome of the campaign by Toyotomi Hideyoshi known as the Subjugation of Kyūshū, the Shimazu clan surrendered. In 1590, Tadamitsu traveled to Kyōto as a hostage sent by his grandfather, Niiro Tadamoto, and resided in Fushimi. Later, Tadamoto’s younger brother, Niiro Tadasuke, took his place so Tadamitsu returned to Satsuma.