The Kira were descended from the Taira clan, settling in Tosa Province in the 15th century. They were vassals of the powerful Ichijo clan, who ruled over Tosa. The Kira clan became friends to the Chosokabe clan of Kunichika Chosokabe, and Ietoyo Kira became a vassal of the Chosokabe after helping to overthrow the Ichijo in 1545. The Kira clan soon lent soldiers and generals to the Chosokabe, and Ietoyo's nephews Mototsura Kira and Kagetsugu Kira served in the Chosokabe Army under Sanefusa Chosokabe in 1547. The Kira clan continued to be loyal retainers until the conquest of Shikoku by the Toyotomi, where the Kira clan crumbled. The Chosokabe were also defeated, but were fit enough to survive as a Toyotomi vassal.