One Piece Chapter 22, page 16: YOU ARE A RARE AND PRECIOUS ANIMAL TOO

Gaimon argues that the One Piece is just a dream, and that anyone who actually found such a treasure would keep it a secret. Luffy remains optimistic, saying he is sure there is a better ending and that he will find it because he is always lucky. Gaimon sighs at Luffy's stubborn confidence and offers to explain why he cannot leave the island.