Boukensha-tachi: Gamba to 7-hiki no Nakama

Gamba, an adventurous mouse, embarks on a journey with his childhood friend Bobo. They gather experienced mice sailors at a harbor. They encounter Chuuta, a mouse who has been injured and in need of help. He appeals for Gamba and Bobo to assist him in defending the island of Yumemishima and its inhabitants from the cruel and wicked weasel Noroi.