Gold Roger was known as the "Pirate King," the strongest and most infamous being to have sailed the Grand Line. The capture and execution of Roger by the World Government brought a change throughout the world. His last words before his death revealed the existence of the greatest treasure in the world, One Piece. It was this revelation that brought about the Grand Age of Pirates, men who dreamed of finding One Piece—which promises an unlimited amount of riches and fame—and quite possibly the pinnacle of glory and the title of the Pirate King. Enter Monkey Luffy, a 17-year-old boy who defies your standard definition of a pirate. Rather than the popular persona of a wicked, hardened, toothless pirate ransacking villages for fun, Luffy's reason for being a pirate is one of pure wonder: the thought of an exciting adventure that leads him to intriguing people and ultimately, the promised treasure. Following in the footsteps of his childhood hero, Luffy and his crew travel across the Grand Line, experiencing crazy adventures, unveiling dark mysteries and battling strong enemies, all in order to reach the most coveted of all fortunes—One Piece. [Written by MAL Rewrite]

Living in the slums of a wealthy town, Rudo and his foster father Regto try to coexist with the rest of the town's residents, but Rudo despises the wastefulness of the upper class. Ignoring the warnings from those around him, Rudo regularly rummages through the town's garbage in search of anything useful or valuable to save from the "Abyss"—a massive hole where anything considered trash is dumped, including people. Rudo's biological father was one such person, having been thrown into the Abyss after he was accused of murder. One day, after running into a mysterious figure on the way home, Rudo returns to find Regto's dying body on the floor. He is immediately found at the scene by the authorities and is charged with murder. No one believes his claims of innocence, and he is thrown into the Abyss. Instead of dying, however, he finds himself in a strange, foul-smelling place surrounded by monsters made out of trash. When Rudo is attacked by said monsters, he is saved by a man named Enjin, who reveals himself to be a "Cleaner"—someone who uses special weapons called Vital Instruments to combat these creatures. In order to get his revenge on the one who killed Regto, Rudo reluctantly becomes a Cleaner to fight his way back up and out of the Abyss.

Alma, an autonomous self-learning robot with advanced combat capabilities, was created by two genius scientists, Enji Kamisato and Suzume Yobane, who developed Alma's artificial intelligence and robotics, respectively. After being mocked by their former acquaintances, the duo have worked together in order to show the world their true talents. But even though they cooperate in their work, the two scientists cannot seem to get along in their personal lives. However, despite their constant bickering, Enji and Suzume develop a glint of mutual affection—feelings that do not go unnoticed by their adorable robotic creation. Now curious, Alma starts to question the true nature of her creators' relationship. As she learns more about humanity from those around her, Alma's bonds with Enji and Suzume only grow stronger.