Head of the Echigo Yasuda Clan, son of Yasuda Kagemoto. He served as a vassal of the Uesugi clan and was given Iiyama Castle in Shinano by Uesugi Kenshin for merits in the Battle of Kawanakajima. The "aki", or "existing" character in his name was also bestowed on him by Kenshin.
In 1578 during the war for succession after Kenshin's death, he and his younger brother Yasuda Yoshimoto both supported Uesugi Kagekatsu, while his relatives Kitajou Takahiro and Kitajou Kagehiro (the Kitajou Clan and Yasuda Clan were both descended from the Mouri Clan) supported Uesugi Kagetora. He wrote: "Those who abandon Lord Kagekatsu, our rightful lord, and run to everyone's Kagetora are not descended from true warriors." It is said that Kagekatsu wept tears of joy upon reading his declaration.
He worked to persuade others such as Shibata Shigeie and Ijimino Nobumune to join Kagekatsu's side. In March of 1579, when Kagetora surrendered the castle and headed for the Kantou, he convinced Horie Munechika, master of Samegao Castle, to switch to Kagekatsu's side. Kagetora was cornered and committed suicide, and Kagekatsu won as a result.
It is also said that Akimoto took pity on Uesugi Norimasa's corpse, which was left unburied after his death, and gave it a proper burial.
In order to persuade Shibata Shigeie, Ijimino Nobumune, and other commanders to join Kagekatsu, Akimoto had promised reward such as castles and territory for merit during the war, a promise backed by Kagekatsu. However, he was opposed by other commanders such as Yamazaki Hidenori and Naoe Nobutsuna, who disagreed because these commanders had not joined Kagekatsu at the beginning of the war. Unable to keep his promise, Akimoto committed seppuku.
He was succeeded by his brother Yoshimoto.