A/N: Written for the Day 12: Promises prompt of the #20yearsatsea challenge on tumblr.
Slight spoilers for the end of the Dressrosa arc, though it's also minor canon divergence so...
Unbeta'ed, so apologies in advance for any mistakes!
Liar, liar, liar.
Ace was damn liar.
It had been Luffy's first, childish thought when he'd regained consciousness after Marineford and realized that, yes, his brother - his strong, confident, infallible big brother - was dead.
Because he'd promised - he'd promised! - he wouldn't die, and then, not ten years later, he'd gone and broken it. Right there, right in front of Luffy. Ace had promised, he had promised, and a man didn't make promises he couldn't keep. Not even to protect their stupid, pathetic, weak little brothers who couldn't, who didn't -
"Liar," Luffy whispers to himself, whenever he wakes up from nightmares of heat and lava and blood mixed with Ace's tears. "Liar, liar, liar."
Luffy vows to never lose anyone else to broken promises, and swears to himself that he'll never break his word to those who are precious to him - which is why he doesn't hesitate to give up the tournament for Ace's devil fruit when Traffy gets into trouble with Mingo. Because he, Luffy, had promised - he'd promised Traffy he'd see this through with him, and Traffy was one of his precious people, now, which meant he couldn't lose him, either.
And then, then a man shows up, calling himself Luffy's brother -
Liar
- only…
Only it isn't a lie, because Sabo is here, and and -
And Sabo is alive.
After the battles are all over, Sabo tries to take off while Luffy's still sleeping off his injuries, but thankfully Zoro and Robin convince him to stay until Luffy wakes up so they can actually talk.
(Zoro and Robin are the best.)
Because Zoro and Robin are the best, they also manage to arrange things so that the two brothers have a few minutes to themselves in private outside.
They're alone for all of three seconds before Luffy starts bawling again and launches himself at Sabo, only this time his brother not only catches him, but actually hugs him back.
"You haven't changed at all, huh?" Sabo chuckles, leaning back and looking down at Luffy with misty eyes of his own. "Still my crybaby little brother…"
Luffy sniffles but doesn't dispute it, because even though he's not a crybaby anymore he doesn't care what Sabo calls him, as long as it's still his little brother.
As though reading Luffy's mind, the corners of Sabo's mouth quirk up, then drop again to settle into a sad line. "I'm so sorry, Luffy," he whispers, his grip on Luffy's shoulders tightening. "I'm so, so sorry I wasn't there, I-"
Luffy wipes his face clean. "You're here now," he says plainly, because that's what's important. He isn't alone - he still has one brother left.
Luffy doesn't realize he said the last part aloud until Sabo sucks in a sharp breath.
"You won't ever be alone again," Sabo says. His mouth trembles, then his whole face sets in determination. "It won't be like with Ace. Luffy, I promise-"
Luffy's stomach bottoms out, and he reacts without thinking. "No!"
Sabo stumbles in shock as Luffy shoves him away, feeling like his heart is trying to claw its way up his throat.
Liar. Liar, liar, li-
"No, no, you can't," Luffy chokes, batting away Sabo's hands when they reach for him. "You both can't lie, you can't-"
"Luffy -"
"No! Ace, he promised, he promised he wouldn't die, either, and -"
Sabo makes a choked off, wounded sound, but Luffy doesn't want to look him in the eye, so he turns away instead.
"- he, he lied -"
"Luffy!" Sabo cries, and then there are two arms around Luffy, yanking him back, back against… against his… his big brother's chest.
"Don't lie," Luffy pleads, in the exact same voice he'd used when he'd begged Ace not to die all those years ago, eyes hidden under the brim of his hat.
"I won't," Sabo says, his arms tightening around Luffy.
They stay like that for a few minutes before Sabo finally lets go and turns Luffy around to face him, though Luffy stubbornly keeps his hat down over his face.
"I can't promise I'll never die," Sabo says quietly, hand warm on Luffy's shoulder. "But Luffy, I swear to you - if you ever need me, if you call…." He pushes Luffy's hat back so he can look straight into Luffy's eyes, his face set in determination again. "I'll be there."
Luffy swallows, and feels something in his chest loosen. "Promise?"
Sabo chuckles. "Of course," he says, and then he smiles. And because it's the same beaming smile he remembers receiving over cups of stolen sake, Luffy knows -
"I don't make promises I can't keep."
A/N: Yes, I messed with canon a little so Sabo and Luffy would actually get to talk and hug it out after Dressrosa. I DON'T REGRET IT. *ahem*