Sometimes Sanji catches Luffy gravely staring at his own hands.
They're fleeting moments, off-color patches that weave through the days. They set in with no discernible pattern, never lasting more than the few seconds it takes for Luffy to find whatever he sees there; his fingers twitch, almost in turn, and then disappear into a tightly clenched fist. Then his hands go down, and everything's back to normal.
Sanji only notices because he knows hands, and he knows his nakama, and he knows that Luffy lacks the finesse of a cook, or a mapmaker, or a musician or doctor—he knows that two years ago, Luffy would barely even look at his hands unless it was to make sure they were smashed deep into some shithead's face.
He almost thinks it isn't his business to know; but those two-year shadows hang in his captain's eyes, and he tastes ash when he bites his tongue. He can't chase Luffy's ghosts when they only seem to haunt him for moments at a time. He doesn't even know why they're there.
Until one night, when he becomes very, very sick.
Chopper sits with him through the night; smooths cool rags over his forehead, coaxes bitter medicine down his throat, and murmurs soft, comforting words into his feverish mind. He catches shards of music, a flash of beautiful orange, a powerful arm curved around three swords at his bedside; bottles of cola go flat on his nightstand, propping up piles of books and silly little novelty knick-knacks. And the comfort is full and encompassing, but he keeps waiting to wake up to wide eyes and a big, stupid grin.
At some indiscernible point, his eyes slit open to—finally—see his captain. He's well enough to be oddly relieved, but before he can say anything, he realizes that Luffy is staring at his hands.
And maybe it's because Luffy is worrying him, the little shit, or because his mouth is bitter with ashes, or because he's just been driven entirely insane by fever, but Sanji reaches a shaky hand out and grabs Luffy's wrist, and asks, "Why?"
The fourth finger on his captain's left hand bends slightly inward, twitching almost as though in pain; yet the serious look on Luffy's face is one of neither grief nor anger. In silence, his captain touches the jagged X on his chest, Sanji's knuckles brushing scar tissue as his grip goes with him, and then the two-year shadows sharpen his eyes as he turns them onto Sanji.
"This is yours," he says plainly as he holds his left hand up, fourth finger still bent, as though that explains everything Sanji could ever need to know.
Hoarsely, Sanji whispers, "Aye, Captain."
Because it does.
(Not a week later, Luffy drives a few spines right through his fist while beating up some hedgehog Zoan bastard. Before Chopper is even on the scene, Sanji roughly pulls him to the side and takes his wrist, wiping blood away with his coat sleeve.)
("You idiot," he growls around his cigarette and around Luffy's shishishi. "Take better care of your hands, will you?")