Akazawa Nagatsune served as a senior retainer of the Hosokawa clan.
Nagatsune and his adoptive father, Akazawa Tomotsune, served Hosokawa Masamoto. In the eighth month of 1506, Nagatsune and Tomotsune engaged in the suppression of Yamato Province. In the sixth month of 1507, they acted upon orders of Masamoto to attack Isshiki Yoshiari in Tango Province. In the midst of this battle, Masamoto was assassinated by senior retainers of his adopted son, Hosokawa Sumiyuki, including Yakushiji Nagatada, Kōzai Motonaga, and Takeda Magoshichi, in an event known as the Eishō no sakuran. A counterattack by Isshiki Yoshiari, Ishikawa Naotsune and kokujin from Tango caused Tomotsune to take his own life. Meanwhile, Nagatsune miraculously escaped to later serve as a retainer of another adopted son of Masamoto known as Hosokawa Sumimoto. Months later, Nagatsune served meritoriously in the front lines when Sumimoto endeavored to recapture Kyōto from his brother, Sumiyuki.
In the ninth month of 1507, Sumimoto ordered Nagatsune to attack Yamato Province, leading to the defeat of Tsutsui Junken, Tōichi Tōharu, and Ochi Ienori of Yamato, whereupon Nagatsune occupied Yamato. In 1508, a struggle for succession of the Hosokawa clan broke out between Nagatsune’s lord, Sumimoto, and Hosokawa Takakuni. In the sixth month of 1508, Ashikaga Yoshitane marched upon Kyōto with the support of Ōuchi Yoshioki, the powerful sengoku daimyō from Suō Province. The army expelled Ashikaga Yoshizumi, the eleventh shōgun, and Sumimoto, restoring Yoshitane to power and appointing Takakuni (from the Hosokawa-Yashū clan) as the kanrei, or deputy shōgun. As a member of the faction supporting Yoshizumi, Nagatsune, along with Sumimoto, Hatakeyama Yoshihide, and Furuichi Chōin, fought against the supporters of Yoshitane including Takakuni and Hatakeyama Hisanobu in Kawachi Province, but lost and fled. The men were captured in Hase in Yamato and executed on 8/2 in Kawachi.