Baba Hachizaemon served as a bushō from the Sengoku to early Edo periods.  He was a retainer of the Anayama clan, kunishū, or provincial landowners in the Kawachi territory of Kai Province who, in turn, were retainers of the Kai-Takeda clan.  His father may have been Baba Genjō.  Hachizaemon’s real name was Tadatoki.

According to the Kōyō-gunkan (a military account of the Kai-Takeda clan compiled in the early Edo period), Hachizaemon appears as a notable figure in the Anayama clan but there are no references to his achievements in the era of the Anayama in historical records.

The Kai-Takeda clan was decimated in the third month of 1582 by the Oda army.  In 1587, after the death of Anayama Katsuchiyo, the young head of the Anayama clan, the remnants of the Takeda clan were inherited by the fifth son of Tokugawa Ieyasu named Manchiyo (later known as Takeda Nobuyoshi).  Hachizaemon served as a deputy of Manchiyo.

Hachizaemon’s name first appears in a jointly signed record from 9/9 of Tenshō 17 (1589) issued to members of the Anayama clan directing them, together with the Manzawa and Hosaka clans, to guard Sunpu Castle.

In 1590, after the Tokugawa clan was moved to the Kantō, Hachizaemon accompanied Takeda Nobuyoshi to move to Kogane in Shimōsa Province.  During the period of his stay in Shimōsa, Hachizaemon’s name appears along with the Manzawa clan and other in prohibitions and other documents.

In the eleventh month of 1602, Nobuyoshi moved to the Mito domain in Hitachi Province with a fief of 250,000 koku.  As the head of chief retainers, Hachizaemon, along with the Manzawa, the Obikane, the Kawakata, and the Sano, was awarded 2,000 koku.  In 1603, after the early death of Nobuyoshi, Hachizaemon, in addition to the Manzawa and Obikane clans, exercised arbitrary rule in the clan and came into conflict with the Ashizawa and other members of the bugyōshū, magistrates acting under the direct authority of the Muromachi bakufu.  In the first month of 1604, Hachizaemon was removed from his position by Ieyasu and turned over to the custody of Ōkubo Tadachika, the lord of the Odawara domain in Sagami Province.

On 12/6 of Keichō 18 (1613), in Nakahara in Sagami, while Ieyasu was returning to Sunpu, Hachizaemon made a claim that Tadachika was plotting a rebellion.  Based on this claim, in the first month of 1614, Tadachika was removed from his position as the lord of the Odawara domain which was then followed by a purge known as the Ōkubo Nagayasu Incident.  At the time of the claim, Hachizaemon is said to have been over eighty years old but his whereabouts thereafter are unknown.

Hachizaemon’s daughter died during the period that he resided in Kai.  On 3/11 of Keichō 9 (1604), Hachizaemon went to worship on Mount Kōya in the environs of Kyōto.