Awaya Motochika served as a bushō and retainer of the Mōri clan of Aki Province. Motochika, and his grandfather, Awaya Motohide, were included in the notable Eighteen Generals of the Mōri.
In 1540, upon orders of Ōuchi Yoshitaka, the powerful sengoku daimyō of Suō Province, Motochika joined Mōri Motonari in an attack against Kashirazaki Castle in the Takaya township in Aki. The castle was defended by Hiraga Okisada. After suffering a defeat, he rebuilt nearby Chikurin Temple and entered the priesthood while his eldest son, Hiraga Takamune, became lord of the clan. In the autumn, Motochika made contributions at the Battle of Yoshida-Kōriyama Castle. In 1555, Motochika further demonstrated his military abilities in the Subjugation of Bōchō, an offensive led by Mōri Motonari against the Ōuchi clan in Suō and Nagato provinces that occurred after the Battle of Itsukushima. In addition to his efforts on the battlefield, Motochika excelled in the handling of domestic affairs as a close associate of Mōri Takamoto, Motonari’s eldest son. Motochika, along with Akagawa Motoyasu, Kunishi Motosuke, served as one of the members of the Five Commissioners for the Mōri clan. Motochika died in 1561 and was succeeded by Awaya Motonobu, who also assumed his position as one of the Five Commissioners.