One Piece Chapter 22, page 13-15: YOU ARE A RARE AND PRECIOUS ANIMAL TOO

Gaimon admits he does not know how to read maps, which makes Luffy burst into laughter. Nami takes the map and explains the geography of the world, pointing out the Red Line, the massive continent that splits the world's oceans.

Nami draws a diagram showing how the Grand Line runs perpendicular to the Red Line, wrapping around the entire globe. She explains that it is the most dangerous sea route in the world, and only the Pirate King, Gold Roger, has ever conquered it. Luffy is thrilled, but Gaimon warns them that the Grand Line is known as the "Pirate's Graveyard" and recalls seeing broken, traumatized pirates who returned from it long ago.

Gaimon describes the hollow, lifeless expressions of the defeated pirates he saw, suggesting they encountered something truly horrific in the Grand Line. He warns that the One Piece might be nothing more than a myth, especially since twenty years have passed since the start of the Great Pirate Era without anyone finding it.