When Kanto kanrei (a shogunal deputy for the Kanto region) Fusaaki UESUGI (the Yamanouchi-Uesugi family) died childless in battle in 1466, Fusasada gave his biological son Tatsuwaka (later, Akisada) to the family to comply with a request from Kagenobu NAGAO who was under the orders of Seii taishogun (Barbarian Subduing Generalissimo) Yoshimasa ASHIKAGA, and had Tatsuwaka succeed to Kanto kanrei.
文正元年（1466年）関東管領の上杉房顕（山内上杉家）が子供を遺さずに陣没した際には、征夷大将軍足利義政の命を受けた長尾景信の求めにより実子の龍若（後の顕定）を養子に送り、関東管領に就任させている。