The Detective Memoirs of Chief Straw Hat Luffy
"In an alternate reality world that takes place in 19th century Japan, Luffy acts as a member of the secret police. The story is divided into two halves: in the first, Buggy the Clown makes trouble in the town where Detective Luffy is stationed, and in the second a mysterious girl named Vivi appears. These stories feature cameos from several minor characters in the normal series."