Plot summary:

The series begins with the execution of Gol D. Roger, a man known as the King of the Pirates.Just before his death, Roger announces that his treasure, the One Piece, will be up for the taking, causing the Great Pirate Era to begin. As a result, countless pirates set out to the Grand Line to look for the treasure. Twenty-two years have passed since Roger's execution, and Monkey D. Luffy, a young pirate inspired by his childhood idol and powerful pirate Red Haired Shanks, has since set off on a journey from the East Blue Ocean to succeed Roger and find the legendary treasure. In an attempt to organize his own crew, the Straw Hat Pirates, he befriends a swordsman named Roronoa Zoro and together, they sail off to find the One Piece. They soon meet Nami, a navigator and thief; Usopp, a sniper and a liar; and Sanji, a womanizing chef; leading to confrontations with Buggy the Clown, Captain Kuro and Don Krieg. Later, Luffy encounters Arlong, a fishman and member of the former Sun Pirates who thinks that fishmen are superior to humans. After Luffy defeats Arlong, Nami joins Luffy's crew and the Navy places a bounty on Luffy's head. After making their way through the Grand Line, the group meets Nefeltari Vivi, a princess who wants to help save her country, the Alabasta Kingdom, from the crime syndicate Baroque Works. They later befriend the doctor and anthropomorphized reindeer Tony Tony Chopper while in Drum Island. Luffy:

Monkey D. Luffy is a pirate and the main protagonist of the anime and manga, One Piece. He is the son of the Revolutionary Army's commander, Monkey D. Dragon, the grandson of the famed Marine, Monkey D. Garp, the foster son of a mountain bandit, Curly Dadan, and the adopted brother of the late "Fire Fist" Portgas D. Ace and Sabo. His life long goal is to become the Pirate King by finding the legendary treasure left behind by the Pirate King, Gol D. Roger. He believes being Pirate King means one has the most freedom in the world. He has eaten the Gomu Gomu no Mi. As the founder and captain of the Straw Hat Pirates, he is the first member who makes up the crew, as well as one of its top three fighters. Luffy has a worldwide reputation for causing trouble, challenging the Shichibukai, the Marines, and even a Yonko, committing felonies against, as well as actions which were deemed threatening by, the World Government. He has gained a reputation for being "reckless" and, in some cases, "insane", after causing an incident in Enies Lobby, entering and escaping from Impel Down, and joining the Battle of Marineford. He is, therefore, famous for being the only pirate to not only break into the three most important government facilities, but also escape from all of them alive. Including the fact that he punched a Tenryubito with full knowledge of the consequences, as well as his heritage, has caused Luffy to be labeled as a "Dangerous Future Element", earning the wrath of Fleet Admiral Sakazuki, making the Marines among his greatest enemies. These acts, amongst other things, have given him his current bounty of 400,000,000, one of the highest past or present bounties in the series. Having had a bounty of 300,000,000 prior to his arrival at the Sabaody Archipelago, Luffy was one of eleven rookie pirates who had been referred to as "The Eleven Supernovas", the eleven pirates with bounties over 100,000,000 to have reached the Red Line.

One Piece offcial site