Upon hearing about the story of Treasure Island, Nobita dreams of discovering and exploring his own treasure island, despite the fact all of the Earth has been mapped already.

Doraemon provides Nobita a special treasure map that shows him the location of a treasure island. At the same time, the media announces the discovery of a completely unknown island. Believing the new island is the treasure island, Nobita recruits Doraemon and Shizuka to journey with him, with Doraemon providing a ship. Gian and Suneo also tag along. However, as they get near the island, they are suddenly attacked by a gang of pirates.

(Source: Wikipedia)