Awaya Motosuke served as a bushō from the Sengoku to early Edo periods.  He was a hereditary retainer of the Mōri clan.  In the Edo period, Motosuke served as the chief retainer of the Kudamatsu domain (later known as the Tokuyama domain) of Suō Province, a branch of the Chōshū domain.

In 1556, Motosuke was born as the eldest son of Awaya Narikata, a hereditary retainer of the Mōri clan.

In 1603, he was appointed to serve as a mentor for Mōri Naritaka who was born in the prior year.  In 1604, he became a chief retainer and, along with Nagoya Mototada, Fukuma Motomichi, and Enomoto Motonobu, attended to Naritaka.

In 1612, his younger brother, Gobei, died of illness.  On 11/2, Motosuke had his third son, Motonori, inherit Gobei’s family and 200 koku in the Kibei neighborhood in the Kotō District of Nagato Province.

On 4/28 of Genna 3 (1617), the Kudamatsu domain was established following recognition by the Edo bakufu of the territory of Naritaka.  At this time, Motosuke received a 打渡坪付帳 from Ibara Motomichi of the Hagi domain.  On 7/9, Mōri Terumoto and Mōri Hidenari (father and son) recognized the succession by Motonori to Motosuke’s fief of 307 koku.

Motosuke died on 5/14 of Kanei 7 (1630) at the age of seventy-five.  A fief of 200 koku was allocated to his eldest son, Mokunojō, but he died early of illness, so Motosuke’s fief of 500 koku in the Kudamatsu domain was inherited by his second son, Takakata, who served Naritaka from his youth.