Boukenkyou Jidai

This is an adventure Manga where a Japanese sword boy travels throughout the world in pursuit of a treasure map.

In 1876, Arashi Takonosuke, an envoy of the Edo Government, departs for Washington carrying a secret message concerning Japan-US trade. However, attacked by pirates in the Caribbean Sea, his boat is capsized. Takonosuke and some survivors are given half of Napoleon's treasure map from the British pastor Picar. But they are swallowed and scattered by a powerful tornado, and blown away to the Nevada Desert.

In the Nevada town, a bar owner, Ham Egg finds out about this story, and searches for the owner of the map. Outlaw Wild Bill Hecock, a mysterious gentleman, Count Monte Christ and others appear successively, causing a great deal of commotion over the treasure map.

(Souce: tezukaosamu.net)