Ietoyo Kira was born in 1509 in Tosa Province to a senior clan loyal to the Ichijo clan, the Kira. He was loyal to the Chosokabe clan after their rebellion against Fusamoto Ichijo, the head of the Ichijo clan, becoming a general of the Chosokabe's daimyo Kunichika Chosokabe. When Kunichika was struck down in battle, Ietoyo became regent to the family, alongside the widow Naomi Chosokabe, whom he was believed to have had an affair with. Ietoyo faced an invasion by the Kono clan of Iyo Province, to the north of Tosa, who wanted to take advantage of the death of Kunichika. He used brilliant tactics to win the Battle of Kochi, which took place outside of the Chosokabe capital. Ietoyo placed his Yari Ashigaru (spear infantry) in front of his Chosokabe Bow Ashigaru, who harried the enemy before they even joined battle with the spearmen, who finished them off. He killed both of the Kono commanders (Michinao Kono and Yorikata Kono) in battle, and gained everlasting glory and honor. He also served under Sanefusa Chosokabe, the son-in-law of the late Kunichika, yet without further distinction. He continued fighting even as an old man, and was killed in the Subjugation of Shikoku by the Toyotomi.