Bouken-tachi Gamba to Nanbiki no Nakama
The Adventurers Gamba and his Seven Friends
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)