They had been working on the treehouse for two weeks, scavenging materials off the Grey Terminal and "borrowing" the rest from the bandits, and now they were almost done. Ace and Luffy worked on securing the last few boards when Sabo came in carrying an enormous piece of black fabric.

"Guys, we need a flag."

Ace dropped his end of the board near immediately and picked up one end of the fabric, leaving Luffy struggling on the floor under the sudden weight.

"This is huge! Where did you get this?" he asked.

"Um…" Sabo scratched his head. "I found it lying around in the Terminal. I think it used to be someone's curtains, though why anyone would want black curtains is beyond me. We need paint."

"Right, I think I saw some up at Dadan's, I'll go get it and you stay here and cut it to a better size."

The last part was shouted, as Ace was down the hatch and running through the trees faster than one could say "watch out for tigers". Sabo was left to rescue Luffy from the board and to look for their only working pair of scissors. Only after a few seconds did he realize something was wrong.

That Luffy had been quiet until then was not such a surprise, seeing as he had had a board lying on his face, but normally he would have started talking the second he was freed. Instead, he sat staring at the old curtains with a look of utter confusion. Confusion was one of Luffy's most regular expressions, right after Happy and Panic, and it was usually much easier to deal with the cause of confusion than the cause of panic.

"What're you wondering about?" Sabo said.

"Why is't so important to have a flag?"

Sabo dropped what he was holding and stared. He knew Luffy was sort of an idiot, but really?

"You don't know?"

Luffy only shook his head, so Sabo sighed and sat down. Then he tried to figure out how to explain this to his youngest brother.

"Okay, so. Do you know who has flags?"

"Pirates!" Luffy answered immediately, and Sabo smiled.

"Yes, who else?"

"Um…" This was a rather hard question, but Luffy did eventually manage to think his way to an answer. "Countries?"

"Exactly. Officially, flags are the symbols of countries. Now, the thing about countries is that they're big, right? Lots of people." He paused, and Luffy nodded, showing that he understood. "Since there are so many people it's impossible to know all of them."

"Why?"

Of course Luffy would have problems with not being able to have unlimited friends.

"Because there are so many, even if you got to know one hundred people every day, you would be an old man before you met half of them."

Luffy reluctantly accepted that.

"Anyway, so in every country there is a bunch of people who've never even met each other, but they're still part of the same country, so they need to have some kind of connection. So instead of having one guy who's friends with everyone, they have the flag, see? Only people who are part of the country can fly the flag, or in some cases people who are allies- uh, friends of the country can too. Also, if you hurt the flag you sorta hurt the entire country, which is why burning a flag is a good way to start a war. With me so far?"

Luffy nodded enthusiastically, and from the light in his eyes, it looked as if he really was stating to understand.

"So, pirates aren't part of any country, so they have their own flags, but it's pretty much the same thing. Your pirate flag shows where you belong and who you belong to, whether that flag is the skull and crossbones or an hourglass or whatever you want. More than that, it shows that you're not part of any country. It means you're free. Your flag means your honour and your freedom, and that is why it's important, see?"

"Family too?"

"Family too."

"We do need a flag!" Luffy said as he jumped to his feet and pulled the scissors out of his back pocket, and suddenly preventing a scissor-related catastrophe was more important than talking.

Almost a decade later, when Luffy raised his own, straw hatted Jolly Roger, or protected a flag with his life even if he had no clue whose flag it was, or when he ordered the government flag shot down in full and complete awareness of what it meant, he thought, only for a moment, that he could smell old curtains and the jungle, and hear the voice of one who is long gone.

Because if Sabo hadn't "died", Luffy might have learned how to think. That's a big maybe though. Very big.