Born in 1534, Tadazumi was originally a Shinto priest of Tosa Shrine before he was made a Chousokabe retainer by Motochika, engaged mostly in diplomacy.

He persuaded Motochika to surrender to Toyotomi Hideyoshi during the latter's conquest of Shikoku and later participated in the conquest of Kyuushuu in 1586. After Nobuchika's death in the Battle of Hetsugi River, he went to the Shimazu Clan as an envoy to receive Nobuchika's ashes.

He later administered the area around Nakamura Castle in Hata District and died of illness in the castle aged 67.