Terashima Moritoku's birth year is unknown; he went by the common name Ushinosuke. A former retainer of the Jinbo clan, the shugodai (deputy military governors) of Etchu, he remained active as part of the anti-Oda resistance in Etchu even after the Jinbo's decline. In 1581, in response to Uesugi Kagekatsu's invasion of Etchu, he took up arms and held Tomisaki Castle (also known as Takiyama Castle), but was suppressed by Oda forces and fled to Daido Castle. He continued his resistance against the Oda thereafter, joining forces with Ikko sect followers from Gokayama and other former Jinbo retainers. When Oda Nobunaga was killed in the Honnoji Incident in 1582, Moritoku is said to have joined other local lords in harrying the Oda forces as they withdrew from Uozu Castle amid the ensuing chaos. He died in 1605.

Even after his lord's house, the Jinbo clan, fell, he never gave up resistance against the Oda, rising in arms in response to the Uesugi — a warrior who held to loyalty toward his former lord and a rebellious spirit to the very end.

Tomisaki Castle (Takiyama Castle), where Moritoku made his stand, survives in Fuchu-machi, Toyama City, as a historic site conveying the sphere of influence once held by the Jinbo, Etchu's shugodai clan. Moritoku's life of continued resistance even after the Jinbo's fall reflects the complex movements of Etchu's local lords in the closing years of the Sengoku period.