Lifespan: Eishō 2 (1505) to Tenbun 18 (1549)
Lord: Matsudaira Kiyoyasu → Matsudaira Hirotada
Father: Abe Sadatoki
Siblings: Sadayoshi, Sadatsugu
Wife: [Consort] Daughter of the Hoshiai clan
Abe Sadayoshi served as a retainer of Matsudaira Kiyoyasu and Matsudaira Hirotada.
In 1535, Sadayoshi and his son, Abe Masatoyo, joined Matsudaira Kiyoyasu, lord of Okazaki Castle in Mikawa, in an attack on Moriyama Castle in Owari Province. The castle was defended by Oda Nobumitsu, the younger brother of Oda Nobuhide. The action intended to address the threat of attacks on the Matsudaira by the Oda. In the midst of this battle, a rumor circulated that Sadayoshi was colluding with Oda Nobuhide to launch a rebellion. While this may have been an artifice of Nobuhide, Kiyoyasu did not trust Sadayoshi and believed the rumor to be true.
Resigned to the situation, Sadayoshi informed Masatoyo that Kiyoyasu may purge him, and entrusted Masatoyo with a letter proclaiming his innocence. On 12/5 of 1535, after hearing a disturbance by the horses in the camp, Masatoyo mistakenly concluded that Kiyoyasu had punished his father, whereupon he promptly cut-off Kiyoyasu’s head. Masatoyo was in turn immediately slayed by Uemura Ujiaki. This incident is known as the Collapse at Moriyama (Moriyama kuzure). Upon hearing of the act committed by Masatoyo, Sadayoshi attempted to kill himself, but was forgiven by Matsudaira Hirotada, Kiyoyasu’s son and lineal heir, and continued in service as a retainer of the Matsudaira.
Kiyoyasu’s sudden death led to confusion within the Matsudaira clan. Matsudaira Nobusada, Kiyoyasu’s uncle and head of the Sakurai branch of the clan, closed in on Kiyoyasu’s younger brother, Nobutaka, and seized Okazaki Castle. Kiyoyasu’s son, Hirotada, was only around ten years of age at the time, and although the lineal heir, could not deter Nobusada from his plans. With the help of Kira Mochihiro, Hirotada fled to Ise Province. Following Mochihiro’s demise, Hirotada drew upon Imagawa Yoshimoto and his men from Suruga Province for assistance. In 1537, Nobutaka, Matsudaira Yasutaka, and Ōkubo Tadayoshi joined Hirotada in a plot to retake Okazaki Castle. Sadayoshi served as a deputy of Hirotada in the plot.
Nobutaka supported Hirotada, but snatched from his younger brother, Yasutaka, Miki Castle and the surrounding territory. Hirotada then decided to take action against Nobutaka, and with the permission of Imagawa Yoshimoto, was allowed passage to attack and expel Nobutaka from Miki. Following the death of Hirotada, Sadayoshi served as commander of the forces stationed at Okazaki when the young Matsudaira Takechiyo (later Tokugawa Ieyasu) was taken hostage by the Imagawa.
Sadayoshi died in 1549. Bearing deep responsibility for the killing of Kiyoyasu by his son, he did not have a successor, meaning the end of his lineage. Nevertheless., after his death, his pregnant wife from the Hoshiai clan married into the Inoue clan, and gave birth to Inoue Kiyohide. Meanwhile, the family lineage of Abe Masakatsu flourished, and his nephew, Shigetsugu, became a member of the council of elders to Tokugawa Iemitsu, the third shōgun in the Edo period.