Head of the Iwaki clan, lords of Iwamae district in Mutsu Province. The Iwaki were a distinguished family who had wielded power in the Iwaki region of Mutsu (present-day Iwaki City area, Fukushima Prefecture) since medieval times. He took Date Masamune's younger sister Otono-kata as his official wife, outwardly forming a kinship tie with the Date. However, amid the fierce power struggles of Oshu, the Iwaki joined the anti-Date southern Oshu coalition alongside the Soma, Ashina, and Satake, repeatedly alternating between confrontation and accommodation with the Date. After Toyotomi Hideyoshi's Oshu settlement of 1590 he had his domain confirmed and gained a temporarily stable footing. However, at the Battle of Sekigahara in 1600 his alignment with the Western army (Ishida Mitsunari's side) proved fatal: after the battle Tokugawa Ieyasu stripped the Iwaki of their domain. He reportedly died young at thirty, and his early death contributed to the effective end of the Iwaki line. Later, part of the Iwaki domain was divided when Satake Yoshinobu was transferred to Akita, and a narrow path toward the clan's eventual restoration was opened.

A pragmatic lord who, despite his kinship with the Date, sought his own survival strategy according to circumstances. His fatal choice at Sekigahara is emblematic of the small daimyo of the late Sengoku era.

Though the Iwaki were dispossessed after Sekigahara, a Satake-branch Iwaki was later revived as lords of Iwakidaira. Tsunetaka is remembered as a south-Oshu lord who sought his own path despite ties to the Date, illustrating the complex politics of the late Sengoku era.