Takahashi Okimitsu served as a bushō during the Sengoku period. Okimitsu was the head of the Iwami-Takahashi clan, a kokujin, or provincial landowner, in Iwami and Aki provinces.
In 1503, Okimitsu is considered to have been born as the son of Takahashi Hiroatsu (the second son of Takahashi Hisamitsu). The genealogical chart of the Takahashi clan, however, has given rise to other theories, so this is not certain.
In 1515, owing to the death in battle of his uncle, Takahashi Motomitsu, who was the head of the Takahashi clan, Okimitsu succeeded him while his grandfather, Takahashi Hisamitsu, served as his guardian. Similar to his father, Okimitsu received one of the characters from the name of Ōuchi Yoshioki, but these ties weakened the unity of the kokujin ikki in Aki to protect the interests of landowners, enabling the Ōuchi to reinforce their influence in the province.
Okimitsu’s aunt (the daughter of Hisamitsu) wed Mōri Okimoto, the head of the Mōri clan, a neighboring kokujin, and gave birth to Mōri Kōmatsumaru. Okimitsu thereby maintained friendly relations with the Mōri. In 1516, Okimoto died and, with respect to succession by Kōmatsumaru, Okimitsu intervened in the Mōri clan in his capacity as a material relative. In 1521, Hisamitsu, who had wielded authority as the maternal grandfather of Kōmatsumaru, was killed in action.
Kōmatsumaru died on 7/15 of Daiei 3 (1523) and was succeeded by his guardian, Mōri Motonari. Motonari had a gradual falling out with the Takahashi clan. On 12/21 of Kyōroku 1 (1528), Motonari (aligned with the Ōuchi), along with Wachi Toyosato, and Hironaka Takakane, laid siege to Matsuo Castle in the Takamiya District of Aki defended by Okimitsu’s father, Hiroatsu. On 5/2 of Kyōroku 2 (1529), the castle fell.
Okimitsu holed-up in Fujikake Castle in Asuna in the Ōchi District of Iwami, and called upon Enya Okihisa (the third son of Amago Tsunehisa) to send reinforcements, but Mōri Motonari had lured Okimitsu’s uncle, Takahashi Morimitsu, to his side, and had him compel Okimitsu to take his own life. Motonari took this as an opportunity to annex the territory of the Takahashi clan. As a result, the Iwami-Takahashi clan was extinguished. Immediately thereafter, Morimitsu was murdered by Motonari on the grounds that Morimitsu had killed his lord.
With respect to the death in battle of Motomitsu and Hisamitsu, there are episodes similar to the demise of Okimitsu, so it is surmised that there was confusion in the transmission of these stories. Meanwhile, Honjō Tsunemitsu, who was similarly eliminated by Motonari, was said to have been a member of the Takahashi family.