Bouken-tachi Gamba to Nanbiki no Nakama / 冒険者たち ガンバと7匹のなかま

When a badly injured mouse staggers off a ship in Tokyo Harbor, he tells the local mice that he has escaped from Devil's Island, where Noroi, the evil white weasel, has crushed the mice with his reign of terror. Tough-guy Gamba rashly promises to help depose Noroi. (Source: The Anime Encyclopedia)...