Akamatsu Norisada served as a bushō and lord of Nawa Castle [in Kōzuke Province].
In 1484, Norisada became a deputy district governor after his father, Uno Masahide, engaged in the rite of tonsure. Norisada resided in Kyōto in 1492. Akamatsu Masanori, the head of the primary Akamatsu clan, died in 1496. Norisada then joined Uragami Norimune, Bessho Noriharu, Kodera Norimoto, and Yakushiji Takayoshi to request approval from the bakufu for Saematsumaru (later known as Akamatsu Yoshimura), Masanori’s adopted son from the Akamatsu-Shichijō branch of the family, to become the successor. Initially, Saematsumaru became the ostensible head of the clan, but owing to his young age of eight, authority was wielded by his guardian, Uragami Norimune. This gave rise to the East-West Battle of Harima (Tōzai-toriai kassen), a struggle among three factions within the clan regarding the issue of succession. One faction supported Yoshimura as originally planned, another group led by Uragami Murakuni backed Akamatsu Katsunori, while a third faction, including Masanori’s widow (Tōshōin), supported Bessho Noriharu. This conflict is also known as Katsunori’s coup d’état. In the end, Saematsumaru remained as head of the clan while Tōshō-in exercised significant influence as evidenced in writings signed in her name. Norimune experienced a decline in power. Norisada was associated with Shimotsuke branch of the Akamatsu, who expanded their influence. In the third month of 1499, Norisada brought Saematsumaru to Shioya Castle to be under the protection of Norimune and the Shimotsuke branch. Meanwhile, Norisada’s father, Uno Masahide, traveled to Kyōto and secured support from the bakufu to mediate an end to the conflict over succession.
In 1525, Norisada was killed by his grandson, Akamatsu Murahide, at Tatsuno-Keirōzan Castle. Murahide was known as a person of integrity, so the reasons for this assault remain uncertain. This may have been an outcome of the discord that beset the Akamatsu clan over a long period of time.