Okubo Hikozaemon, or Tadataka (1560-1639), became perhaps the most popular member of the samurai class during his lifetime.
The eighth son of Okubo Tadakazu, Hikozaemon never attained the great status of his elder brothers, two of whom became daimyo while he was still a boy. In 1575, at the age of 15, he fought bravely in the battle of Nagashino, after which he was engaged by Tokugawa Ieyasu. He fought his last battles in the 1614 Winter and 1615 Summer campaigns at Osaka Castle, being made a commander of a company of spearmen at the former, and thereby a direct retainer of the shogun with the relatively low income of 1000 koku of rice. Ieyasu placed great reliance on him. It is popularly believed that the shogun left an instruction in his will saying that he forgave Okubo his insolence and stubbornness, and that future daimyo should consult him over any doubts or divisions. Okubo is said later said to have been humorously refered to as "The Office of Government Opinion." He endeared himself through his writings, notably the Mikawa monogatari (Tale of Mikawa), written for the private moral guidance of his family. But the book was secretly copied and distributed among the samurai and townsmen. It records the rise to power of the Tokugawa and the role that his own Mikawa clan played in the process. He instructs his successors not to respect Iemitsu too much, since he would order them to commit suicide over the slightest fault. His behavior was both direct and eccentric, but he always supported those in reduced circumstances. On one occasion, it is said, since those below the rank of direct vassal to the shogun (hatamoto) were prohibited from riding in palanquins, which he thought unfair to people with disabilities, he had himself carried to Edo Castle in a large washtub. In 1632, Iemitsu gave Okubo the rank of Standard Bearer, and he was allowed finally to ride on horseback in procession with a small retinue of fifteen foot soldiers (ashigaru). When he was offered a further increase in income in his old age, he is said to have refused it as it had come too late.
The provenance of the helmet is recorded in the intriguing letter written by one Shinsui Yoshio in 1920, which accompanies the lot, and which is refered to in the NBTHK certificate that authenticates the helmet. In 1630 Kawai Matagoro killed Matsudaira Gendayu over a minor matter. Gendayu's brother Kazuma was brother-in-law of Araki Mataemon (1598-1638), and the two determined to take revenge by killing Matagoro, who had fled to Edo. Okubo Hikozaemon, fearing that the feud could escalate, decided to intervene. He asked a retainer of the Hitoyoshi fief in Kyushu named Shibuya to take Matagoro under his protection. To emphasize the request, Okubo sent Shibuya his own clothes and the present helmet. Kazuma and Araki pursued Matagoro for four years, eventually catching him in 1634 in the well-known "Revenge of Iga Castle," in which twenty-nine persons lost their lives. The helmet remained in the posession of the Shibuya clan until the Meiji period, eventually to be acquired Shinsui Yoshio.