Chapter 585 is titled "Brothers' Sake Cups".
Sabo is revealed to be a Noble - a status he detests and the reason he had run away from home. However, Luffy and Ace do not care about Sabo's status, and the trio spend many happy days together. The three share sake cups and become sworn brothers. However, their days together are abruptly cut off when Bluejam, being paid by Sabo's father, forces Sabo to give himself up to his father in order to save Ace and Luffy.
The boys are unaware of that the World Nobles are coming and continue to train and run around the mountain, getting stronger by the day. It is then that more information about the geography of the land is revealed. Beyond the Gray Terminal there is an area known as the Great Gate which is part of a wall to another area called the Goa. Foosha Village is also part of this kingdom though it is largely forgotten due to the mountains around the area. The kingdom is broken up into sections: The Edge Town, which is still near the Gray Terminal through has buildings and is home to delinquents and hoodlums, the Town Center where the middle class live, and in the center guarded by another high wall, is the High Town where the royals and nobles live. Goa is said to be the most beautiful country in the East Blue even though it is segregated due to the class system.
The three boys sneak past the Great Wall one day during the regular trash dumping into the Gray Terminal, and go into the Town Center and pull a dine and dash. They escape out the window of a diner and run from the guards. However, one of the citizens recognizes Sabo and calls out to him, but Sabo just ignores the man. While running, they ask if Sabo heard the man calling his name. Sabo bluntly replied no and that they must have mistaken him for somebody else. Once back in the forest, Ace and Luffy demand to know if Sabo has been keeping anything from them. After a some goading, Sabo comes clean and reveals that he is actually a noble who ran away from home. The reason behind it was that his parents always pressured him and were more concerned about their finical and noble security and position than their son, making Sabo feel like a burden with no one in the world who cared for him. This is why he wants to become a pirate as he wishes to be free from their overbearing rule and write a book about his adventures. Ace and Luffy agree wholeheartedly, with Ace declaring that he'll be famous and he will prove that his life is worth something. Luffy also declares something, but it is not shown, only Ace and Sabo's shocked reactions. Ace pulls out some alcohol and pours some into three sake cups, claiming that from that day forward the three of them were brothers.
And from day to day they kept getting stronger, fighting pirates, taking baths together, eating together (not to mention shoving Dadan and crew out of the food), and saving one another during their trips across the mountains. Makino and Woop Slap would occasionally come by and drop off new clothes for them. They would fight against the wild animals of the forest and bring them home to eat, Garp would visit and beat them senseless. They built their own treehouse and lived in it and generally acted the way boys their age should act. But one day Sabo's father found them and, with the assistance of the Bluejam Pirates, captured the three with Sabo's father claiming that Ace and Luffy lured him away from home. Just as the Bluejam were about to beat Ace and Luffy. Sabo willingly decided to go back with his father in order to save them, though with great reluctance. Ace and Luffy could do nothing more but beg him to stay and come be a pirate with them as he was led away.
- On Hannyabal's shirt is written the word 昇格 (Promotion) (on the cover page).
- This chapter shows Luffy performing his signature move, the Gomu Gomu no Pistol for the first time as a child. Although he had not perfected it yet during that time as it was his first try.
- Luffy has lost to Ace and Sabo 50 times each.
- On Ace's shirt is written the word 無罪 (Innocence) page 3 and 暴力 (Violence) page 8.
- Sabo is revealed to be the son of a noble.
- In Chapter 558, there is a short flashback about the drinks being poured, with Luffy having a bandage on his nose. To keep this going, this chapter did the same. But in the rest of this chapter, Luffy has bandages on his forehead and on his cheek; not on his nose.
- Sabo, Luffy, and Ace become "brothers".
- Each brother reveals their life goals:
- Sabo wants to write a book about the world.
- Ace wants to become a world-famous pirate in order to prove his worth.
- Luffy's goal is left unrevealed, but Sabo and Ace apparently find it unbelievable.
- Sabo gives up his freedom to save Ace and Luffy.