The song is most likely “Kaze wo Sagashite” , which is the One Piece opening used around episode 426.

A few useful notes:

  • The title is often written as “We Are! - Kaze wo Sagashite” in some listings.
  • If you meant a background guitar piece from the episode rather than the opening, the exact track can vary by scene and is harder to identify from the episode number alone.

If you want, I can also help identify the specific scene music from episode 426.