One Piece fans know filler can be a graveyard, but this one understands the only reason to exist: letting these characters breathe in a place where the story doesn't matter. Edo-period Luffy as a detective is not a new idea, but watching him solve problems with the exact same stubborn logic he uses to pick fights feels earned because the cast around him, the ones the main series forgot, finally get a moment. A special built for people who stayed, not for people discovering the show.

Luffy serves as a detective in the Grand Jipangu, an alternate take on the Grand Line styled after 19th century Japan. The special tells two stories. In the first, Buggy the Clown stirs up trouble in the town where Luffy is posted. In the second, a mysterious girl named Vivi turns up. Along the way, characters from across the series make cameo appearances. The result is a comedic adventure detour that sets aside the usual storyline for a playful alternate universe.