In March 2026, One Piece hit 600 million copies sold, so creator Eiichiro Oda wrote the series' true secret on paper, tore it in half, ran the top half in newspapers, and sank the answer half—sealed in a chest—651 meters into the sea, to be raised only when the story ends.

In February 2026, One Piece creator Eiichiro Oda wrote the story's central secret on paper for the first time. Sealed in a chest and pressure-resistant glass sphere, it was placed 651m underwater with guidance from JAMSTEC and is due to be revealed after the comic ends.