The series focuses on Monkey D. Luffy, a young man who, inspired by his childhood idol and powerful pirate “Red Haired” Shanks, sets off on a journey from the East Blue Sea to find the famed treasure One Piece and proclaim himself the King of the Pirates. In an effort to organize his own crew, the Straw Hat Pirates, Luffy rescues and befriends a swordsman named Roronoa Zoro, and they head off in search of the One Piece. They are joined in their journey by Nami, a navigator and thief; Usopp, a sniper and a liar; and Sanji, a womanizing chef. They acquire a ship named the Going Merry and engage in confrontations with notorious pirates of the East Blue. As Luffy and his crew set out on their adventures, others join the crew later in the series, including Tony Tony Chopper, a doctor and anthropomorphized reindeer; Nico Robin, an archaeologist and former assassin; Franky, a cyborg shipwright; Brook, a skeletal musician and swordsman; and Jinbe, a fishman helmsman; and they also acquire a new ship named the Thousand Sunny.
The world of One Piece is populated by humans and many other races such as “fishmen” (a race of fish/human hybrids, similar to mermen and mermaids), dwarves, Minkmen (a race of humanoid animals), and giants. It is covered by two vast oceans, which are divided by a massive mountain range called the Red Line, which is also the only continent in the world. The Grand Line, a sea that runs perpendicular to the Red Line, further divides them into four seas: North Blue, East Blue, West Blue and South Blue. Surrounding the Grand Line are two regions called Calm Belts, similar to horse latitudes, which experience almost no wind or ocean currents and are the breeding ground for huge sea creatures called sea kings. Because of this, the calm belts are very effective barriers for those trying to enter the Grand Line. However, navy ships, members of an intergovernmental organization known as the World Government, are able to use a sea-prism stone to mask their presence from the sea kings and can simply pass through the calm belts. All other ships are forced to take a more dangerous route, going through a mountain at the first intersection of the Grand Line and the Red Line, a canal system known as Reverse Mountain. Sea water from each of the four seas runs up that mountain and merges at the top to flow down a fifth canal and into the first half of the Grand Line. The second half of the Grand Line, beyond the second intersection with the Red Line, is known as the New World.
The currents and weather of the Grand Line’s open sea are extremely unpredictable, whereas in the vicinity of islands the climate is stable. The magnetic fields within the Grand Line cause normal compasses to malfunction, making it even more difficult to navigate, and instead a special compass called a Log Pose must be used. The Log Pose functions by locking on to one island’s magnetic field and then locking on to another island’s magnetic field. The time for it to set depends on the island. This process can be bypassed by obtaining an Eternal Pose, a Log Pose variation that is permanently set to a specific island and never changes.
The world of One Piece includes anachronisms, such as the Transponder Snail, snail-like animals that can be attached to electric equipment and function as rotary phones, fax machines, surveillance cameras, and similar devices. Dials, the shells of certain sky-dwelling animals, can be used to store kinetic energy, wind, sound, images, heat, and the like and have various applications.
A Devil Fruit is a type of fruit that, when eaten, grants a power to the eater. A person may only eat one Devil Fruit during their lifetime, as eating a second devil fruit will swiftly end their life. There are three categories of Devil Fruits;
- Paramecia is a category of fruits that give the user superhuman abilities.
- Zoan fruits allow the user to fully or partially transform into a specific animal. As well as real-life animals, some Zoan fruits allow the user to transform into mythical creatures. Through an unknown technique developed by Dr. Vegapunk, certain items can “eat” a Devil Fruit like Mr. 4’s Bazooka Lassoo, Spandam’s sword Funkfreed, Caesar Clown’s pet slime Slimy, and non-canon items like Shuzo’s bazooka Alpacacino and Patrick Redfield’s pen Pato.
- Logia fruits give control over, and allow the user “to change their living body structure into the powers of nature”.
Devil Fruits are said to be incarnations of the sea devil himself, and as a result, Devil Fruit users cannot swim in sea water, as “they are hated by the sea”. Sea-prism stone also has this effect. When even partially submerged in sea water, they lose all their strength and coordination, although some abilities remain. For example, Luffy is still able to stretch after being totally submerged. Moving water, such as rain or waves, does not have this effect. When a Devil Fruit user dies, the powers reincarnate into a new Devil Fruit. For unknown reasons, Devil Fruit users cannot eat a second Devil Fruit because it would cause their bodies to burst, although Blackbeard managed to get a second Devil Fruit power through an unknown method. Devil Fruit powers can be in a stage called “Awakened”, where the user can turn anything around them, besides their own bodies, into what their Devil Fruit power is.
Haki is a latent ability that every living being in the world of One Piece possesses; very few manage to awaken it, and even fewer master it. There are three varieties of Haki: Color of Observation or Mantra allows one to sense the presence of other beings and to have a form of limited precognition. (This is a great advantage in combat because the user can foresee his opponent’s attacks). Color of Arms allows one to envelop body parts and even inanimate forms with a force akin to an invisible armor that possesses defensive and offensive properties. It also allows one to inflict harm upon Devil Fruit users. The rare Color of the Conquering King is an ability that, unlike the other two Haki, only a few gifted people have. (If a person is not gifted, then no matter how much they train they will never be able to use it). The Color of the Conquering King enables one to overpower the will of the weak-willed. It can be used to mind-control or even render the victim unconscious. Note that strong willed people can withstand, or even completely ignore, the effects of this Haki, even if they do not possess this ability themselves. This Haki can also have physical impacts, such as causing tremors and destruction to the user’s surrounding area. It is shown that when it is used too much Haki will stop working for certain periods of time, so it can’t be in use constantly.