Complex sentence: In the Sengoku period, Mino "-no kuni" was one of the original provinces controlled by Oda Nobunaga, and his heirs controlled it even after Nobunaga died and Toyotomi Hideyoshi took power.
Split into simpler sentences: In the Sengoku period, Mino Province was one of the original provinces controlled by Oda Nobunaga. His heirs continued to control it even after Nobunaga died and Toyotomi Hideyoshi took power.