Spoilers for the Whole Cake Island Arc

I took some liberties in spreading the information gained in Dressrosa about Sabo to the rest of the crew (I'd imagine that'd be considered semi-important to all of them). Keep in mind :)

Enjoy!

(Disclaimer: I do not own One Piece or any related characters)

To be honest, everyone in the crew had assumed for the longest time that Luffy was incapable of growing ill from a simple virus or cold or anything of the sort.

He seemed so lively all the time, even in the most terrible conditions and had proven himself to be a monster when it came to fights, so everyone left well enough alone when it came to ailments.

Pretty much everyone had grown sick at one point while part of the Strawhat crew. Nami, Robin, and even Zoro had experienced colds at some point throughout their voyage. Chopper deduced that either Nami or Robin had caught something, and proceeded to pass it to the other person since they shared the same room. Sanji proceeded to go nuts at the implication that had with Zoro. The disgruntled man merely suffered silently as far away from the cook as possible for three days straight.

Sanji and Franky had gotten a bug from some food, much to Sanji's horror. They were over it within a week.

And Chopper had caught something particularly nasty from a group of deer on a different island. It was nothing too serious, but it kept him off of his feet for a few weeks.

Brook and Luffy appeared to be the only two who hadn't gotten sick, and for Brook that at least made sense. He was dead, after all. Nothing to really get sick. But, Luffy was amazing in his own way and every one concluded that it was just one of Luffy's whims.

At one point even Chopper had believed Luffy's immune system to be impenetrable to sickness.

And then it happened. So startlingly quick that it left the crew in a panic.

They had just left a winter island with a village filled with sick people. Some sort of virus going around. Chopper had gone alone with Luffy to get supplies as to not risk spreading the illness throughout the crew. Sanji decided to skip on getting food from that island incase it was somehow contaminated, but Chopper needed medical goods— especially considering Zoro had the majority used on him previously in Thriller Bark.

It was two days after they left the plagued island that Luffy collapsed on the grassy deck of the Sunny.

Mahem broke out. Fears of there being a hidden wound or that the wounds from Thriller Bark really were still there— which Zoro immediately shot down with an icy glare.

The bastard just got sick is all, Sanji smiles ruefully at the thought now. How worried they all were— everyone. Seeing someone who's always so jubilant suddenly turn into a limp ragdoll isn't a comforting sight to behold.

Chopper checked Luffy over and lo and behold he had caught the ailment from the plagued island. A simple flu bug. Or, not so simple. In actuality it was a nasty thing that shot the captain's temperature up past dangerous levels and prevented him from being lucid for days on end. Everything Sanji tried to feed him would end up getting thrown back up— which caused a tremor in the cook's hands that would not go away for hours after any effort to feed his captain.

Someone had to be with him day in and day out to keep watch over the sleeping boy and most of the time it ended up being Chopper, and when he needed a break for whatever reason it was Zoro.

Now, Sanji had taken up a spot in the infirmary. Zoro's turn to take watch coupled with Chopper's need to sleep forced Sanji's hand. The uncomfortable stool seemed to make the experience even more unbearable somehow, and Sanji found himself wishing for his turn on Luffy-watch to be over.

It wasn't like he hated being around his captain, but rather he hated being around him like this. So weak and vulnerable. So wrong.

The red cheeks and forehead, the damp hair, the blanket covering everything but those two features. Scrunched eyebrows replacing the space where bright, illuminated eyes usually were, and a grimace where welcoming smiles always derived from.

Sanji chews on an unlit cigarette, staring down at the still form.

"Proved us all wrong, eh, Captain?" he mumbles quietly, picking at his sleeves from where he has his arms crossed, "Seems a flu can knock even you on your ass."

He sighs sadly, picking his cigarette from his mouth and discarding it in the waste bin beside the bed. It takes him two seconds before the silence drives him to run his hands up his tired face and through his tousled hair.

And just like that, once his eyes are uncovered and go to rest on his captain's face once more, he's met with two squinted eyes. Two squinted eyes that stare at the cook for an uncomfortably long time— unwavering and, if Sanji didn't know any better, almost confused.

Sanji finds himself caught between a surprised gasp and a tired sigh, "Good to see you awake, Luffy."

No response, and it takes Sanji a moment to realize that, though Luffy's eyes are open and staring, they're also glossy and rimmed with red. Not all there then. Lost in the plumes of feverish visions.

Sanji grimaces, "Luffy, just go back to—"

As soon as he begins speaking, though, Luffy manages to wrestle the covers from around his shoulders and leverages himself up onto his elbows. Sanji wheels forward on the stool just as his young captain gets himself into a seated position.

Sanji's two hands take a firm hold on Luffy's shoulders. The cook ignores the way Luffy's eyes linger on him in the throes of confusion as Sanji pushes the boy back down onto the bed, "You need to go back to sleep, Luffy," he mumbles more clearly that last time he spoke, making sure Luffy can fully hear every syllable, and proceeds to rearrange the covers back around the squirming captain, "You've gotta feel like shit, so—"

Luffy suddenly stills, and the sensation is odd enough that Sanji wonders if the boy conked out, just as he instructed. He finishes laying the blanket atop Luffy's shoulders before he peers at the younger's face once again.

Nope, not asleep.

But Sanji freezes similar to Luffy. An uncomfortable thing considering the half-standing position he's in. But, the look his captain had previously is gone and is suddenly and eerily replaced with one of disbelieving horror.

Sanji slowly sits down, eyes still stuck in a staring contest with his captain. His body loses its tension but still reserves some incase he has to fend off some sort of violent fever dream. He's seen it happen before, and such a thing wouldn't really surprise him with Luffy of all people.

He tries to act nonchalant. To act normal as to elicit some sort of familiarity. His face is careless when he grinds out, "What—"

"Sabo?"

And then the tension is back.

But as the confusion and uncomfortable feelings wrack Sanji, Luffy's face softens, a small smile that's far more feeling than any of his outrageous and warm ones spreads across his face. His eyes slowly slide closed.

"What'cha doin' here?" Luffy mumbles almost incoherently.

Sanji's mouth bobs like a fish, and he wonders whether he should go get Chopper before the possibility of anything happening happens. But he doesn't, and he finds himself, despite his uneasiness, responding, "Where else would I be?"

"Mmm," Luffy hums, licking his lips as his brow creases beneath the damp cloth on his forehead, "Gone. Glad you're 'ere, though."

And as though Luffy could sense Sanji's discomfort despite the case of misinterpreted identity, he snakes his hand out from under the blankets and reaches a quivering hand towards the cook, expression unchanging.

Slowly, Sanji takes the appendage in his own hand, combing his fingers through the spaces between Luffy's and stays that way.

Even as Luffy mumbles an almost silent, "Missed you."

Even as his captain fades into unconsciousness once more.

Even as Zoro makes his way into the infirmary to take over Luffy-watch hours later— not even daring to mention the spooked look on the cook's face, nor the way he is hunched over the sleeping captain like his body was protecting or hiding something precious.

His fingers feel pried away from something valuable when he leaves, and he finds himself chugging through three cigarettes consecutively on deck as the realization of what 'gone' and 'missed you' might entail, and the hidden memories of this 'Sabo' that lie beyond the glazed, almost sad eyes digging into his mind.

He occupies himself therapeutically that night by preparing to make the largest amount of meat he ever has for when his captain is well enough again.

It happens again, but differently.

It happens because of wounds too hefty to heal without some sort of complication.

Luffy's battle with Katakuri and the consecutive escapade from Whole Cake Island was tiresome and taxing for everyone. Once they were out of the woods and were safely on their way back to meet up with Zoro and the others in Wano, Luffy's body just practically shut down.

Not in a particularly dangerous way. But, in a shock sort of way. In a 'sleep for two days straight with a fever' sort of way, but Chopper wasn't overly worried so Sanji's anxiety was able to ebb away slightly.

Words such as "normal" and "stress" and "needed sleep" pass over him, but they don't help with the slight guilt worming through Sanji's innards. No one, not even Chopper who typically likes staying with his patients himself when they're unwell, oppose Sanji's request when he asks to stay with Luffy that night.

They only pass a knowing glance between each other and go about their business.

And then Sanji's once again sitting in that same stool, looking at his captain in a different light because he's in that bed because of him. Because, by now especially, Sanji should realize that Luffy doesn't simply give up when a nakama is being taken from him. Because, Luffy is an individual willing to tear the world down for the sake of another.

He's witnessed it enough himself, and definitely heard his fair share from others from the times when he was absent. Sanji chuckles to himself, rubbing a hand down his face.

And just like before there are eyes open and watching him from beneath a damp compress and Sanji can't help but feel joy at the sight.

Without any words passing between them, Luffy once again pulls his arm from beneath the blankets and holds it out shakily for the cook to obligingly take. Like he can sense the daunting emotions swimming through Sanji's head without actually recognizing him as himself.

And when Luffy responds to the silence of the room with a breathy "Sabo" and a mumbled "Warm", Sanji takes the offered information from so long ago during another witnessed fever driven illusion, along with what Nami, Chopper, and Brook had been told by Zoro and the others from when they were on Dressrosa, and puts two-and-two together.

Sanji had brothers. They didn't look very much alike when it came to hair, but they were the same age and he'd imagine they shared some common facial features. He cringes at the thought.

Still, laying his gaze on the fingers intertwined with his, much too hot and clammy and scarred and small—how such small hands could be so abused— he realizes something. The warmth that was in his stomach and cheeks, the odd tingling he had when Luffy's face turned to his with a familiar, if tired, smile that spoke of not glee but contentment, and the peace he felt when glassy eyes slide closed… he had never felt so thankful about the idea of brotherhood.

Not his own memories of brotherhood, but Luffy's. To be so relieved in the presence of a sibling—to be so willing to tear the earth apart and reform it for one…

When he saved his family, it was less about love and more about the impending feeling of guilt and the hidden devotion of his blood relations.

Luffy's brotherhood was opposite, though. Not blood. Love.

Sanji's free hand snakes its it's way through the dark locks of sweaty hair, fond gaze lingering on the battered face.

Sanji wonders if there's a reason Luffy rekindles the memories of Sabo when he's there—

With fire licking at Sanji's feet and his lighter; with noble and royal blood evident everywhere around them on the battlefield despite the hatred felt towards his relatives. With golden hair and concentrated eyes.

But, more-so than simply physical appearance—

Thinking to the way he was taken from the crew, how he was metaphorically on the chopping block with his hands tied behind his back— how Luffy had run into the battle without a second thought, arousing conflicts and being beaten to a bloody pulp without a care for himself…

— Sanji thinks there could be.

In which Sanji's back, I still love ASL, and I have feelings, okay?

(Though, on a side note, I just kept coming up with more and more similarities between Sabo and Sanji that I found interesting:

-Both from royal/noble families (of whom they hated)

-Both have blonde, semi-not really-longer hair (the obvious one)

-Both now have fire-based abilities

-Both dress more formal (in blue colors a lot of the time)

-Both are less brutish (i.e. like Ace and Zoro) and more "civilized" so-to-speak (i.e. diplomatic, able to cook, level-headed, etc.)

-Both are considered to be the second oldest brother (on an SBS interview, Oda stated that Sanji would be the second oldest Luffy, one below Zoro and one above Luffy)(Ace is theoretically the oldest of the three ASL since he was born January 1st and is believed to be the same age as Sabo)

-Etc.