The series focuses on Monkey D. Luffy—a young man made of rubber after unintentionally eating a Devil Fruit—who sets off on a journey from the East Blue Sea to find the deceased King of the Pirates Gol D. Roger's ultimate treasure known as the "One Piece", and take over his prior title. In an effort to organize his own crew, the Straw Hat Pirates,[Jp 15] Luffy rescues and befriends a pirate hunter and swordsman named Roronoa Zoro, and they head off in search of the titular treasure. They are joined in their journey by Nami, a money-obsessed thief and navigator; Usopp, a sniper and compulsive liar; and Sanji, an amorous but chivalrous cook. They acquire a ship, the Going Merry[Jp 16]—later replaced by the Thousand Sunny[Jp 17]—and engage in confrontations with notorious pirates.