越中國
In 1582, he and Shibata Katsuie successfully laid siege to Uozu against Uesugi Kagekatsu from the Uesugi clan. He was granted Etchū Province as a reward for helping Shibata Katsuie fight the Uesugi clan. Later in 1582, after Oda Nobunaga's death at Honnō-ji, Narimasa joined Tokugawa Ieyasu.