DISCLAIMER: I do not own anything from Katekyo Hitman Reborn or One Piece.

SUMMARY: There is a reason why the great rookie captain should never cross paths with the reluctant Vongola boss. Having them fight one time was bad enough. Forming an alliance, however, was another thing. AU

NOTE: Where Tsuna and co. are pulled by an eccentric rookie captain to fight alongside during the Whitebeard War. And yes, this is a short story spin-off for my other KHR fiction, Vongola Pirates. As such, this is a bit (okay, maybe more than a bit) KHR-biased. Happy reading!

WARNING: Heavy swearing. Slightly cracked. Unbeta'ed. Short chapters. AU.

WHITEBEARD WAR

by pseudonym08

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Prologue: How It All Started

It was one normal Monday morning for the Vongola lot.

Or so they thought it was.

Calm breeze swept up from the east and all of them, sans one demon prefect and one pineapple-haired illusionist, were enjoying their morning snack on deck, courtesy to Yamamoto. They had just left some unnamed island a few days ago, and apart from getting a new ship they later named Dio Giove, they were able to replenish all the necessary supplies and equipments for their next journey.

Gokudera was seated on the bowsprit, glasses on, small notebook on hand as he kept a critical eye on the weather and his log pose.

With clear skies they have right now, they shouldn't encounter some problems for the next two days or so. Then again, since when had Grand Line weather ever fail to surprise them? Next thing they knew, a storm could be brewing in a few minutes.

Gokudera clicked his tongue. Ahh… whatever, he thought. By this time, they were used to bipolar weathers after all. He was sure they could get past it. The Vongola crew maybe lax most of the time, cut off those random instances Hibari or Mukuro (and most of the time Lambo) would start a fight for no apparent reason, but generally, they could always instantly spring into action the moment the situation calls for it.

As much as Gokudera hated to admit it, they were an excellent team. His captain had recruited passable crew mates. People he can rely on (but sure as hell won't admit it to them on their faces). Troublesome, yes. But still reliable in their own twisted troublesome ways.

With that thought, Gokudera took off his glasses, placed it on its case before shoving it inside his pocket along with the notebook. He'd just leave everything now to fate.

The white-haired self-proclaimed first mate was about to go down on deck and join the others when, with eyes sharp as ever, the figure of a brig sloop caught his attention. Painted on its main sail was the image of a skull with a strawhat.

— Whitebeard War 00 —

"THE MUGIWARA?!" Tsuna panicked. When Gokudera had greeted them with sparkling eyes, the brunette captain had expected he had an island on sight. Tsuna massaged his temples, reminding himself yet again that the people with him weren't in any way normal. As such, their definition of excitement and happiness far contrasted his own.

His crew gave him confused looks.

"What's wrong, Tsuna?" Yamamoto asked, putting down a plate on the table. By this time, Tsuna flipped.

"Don't you remember who the Mugiwaras are?" he asked with a worried panicky tone. The others only stared at him with confused looks.

"They challenged the World Government at Water 7-!"

"-before us-"

"-and was very famous for defeating various enemies-"

"-like us-"

"-and… Wait a minute, can you please stop butting in, Yamamoto-kun?"

Yamamoto scratched his head and laughed. Tsuna grew anxious all the more with this. Everyone was so fucking calm! And complacent. A 'so-what' expression clearly etched on their faces.

"Sorry, Tsuna. I just don't understand. Your bounty's-?"

"That is not the point, Yamamoto-kun." I don't want to die yet, Tsuna mentally added. Roughly translated, he simply wanted to avoid conflicts as much as he can. True, he was confident they could at least survive against the Strawhats Pirate; but, with the wrath of the government finally upon them, not to mention other pirates and pirate hunters close by, Tsuna didn't want to have one more notorious pirate group on the 'people who wanted Vongola dead' list.

"Either way, we must not engage the Strawhats Pirate. I repeat, we must not. That is an or-!"

BOOM!

Before he could finish, faint vibration, though still noticeable to people with monstrous senses as theirs, coursed through Dio as one of their barrels went off.

"What... was that?" Tsuna asked. And paled. He searched the deck. The cow-print-loving kid who was once with them was no longer there.

"Ah- Hahahaha. That was our canon, Tsuna," Yamamoto answered, breaking off the silence.

Tsuna turned around, just in time said canon exploded with another loud Ka-BOOM! on the other end, near the Mugiwara's ship. He was thankful it did not make a direct hit but… in this world of piracy and war, Tsuna knew just that was a hell lot enough indication for challenge.

"Gyahahahaha~"

A resounding kid's laugh echoed from the artillery below.

Tsuna sweat-dropped. He looked at the crew around him. Yamamoto, being the calm one that he is, Tsuna had expected he would at the very least calm Tsuna down or be somewhat against this and think of ways to put this new plight of theirs into a positive one. But to his shock — and absolute horror — beneath that usual cheerful smile of their swordsman lie a smirk and an unspeakable thirst for an incoming fray.

The brunette resisted the urge to bang his head on a nearby pole. He had almost forgotten how much of a fan Yamamoto was on Mugiwara's alleged first mate.

Tsuna hung his head. Gokudera was no better either. The lad was basically excited, more so now that the die has been cast. He immediately pulled out his newly made CAI from nowhere, clearly eager to test them. And Hibari and Mukuro! Tsuna can't even begin to describe them. Both had come out the moment they heard of a possible fight. And both had equally scary faces, contorted looks that could kill, obviously seeking out the inevitable bloodbath.

Lambo was no different either, if the hysterical laugh a while back was any indication. He might've been a coward at times, and downright sloth-y, but his fighting prowess was incontestable despite his age. Perhaps honed by his weird knack of challenging anyone anywhere and anytime with grenades or any armaments he had.

"Extreme!" Now even onii-san had his game face on too.

Mou~! Is he the only sane person on this ship?

How'd he even get here again? Tsuna tried recalling. To have these monsters as crewmates, only for the World Government to lump him together with said monsters, even going so far as labelling him the monster of the monsters at times! Seriously. Everyone is against him. He's just a poor victim here! The people with him are the real monsters. Tsuna mentally cried. He had hoped to pass by the Mugiwara crew unnoticed. Then again… Ahh, damn pirates for robbing him off of his day off. Tsuna scratched his head.

After a split second of last moment hesitation, Tsuna sighed. Then, he finally put on his gloves.

He wasn't going to fight. Really! But… if he wanted to live, if he wanted to protect his friends and the ship, he had to. He won't let them have it their own way. They started it. And so he must find a way to end it, before it develops into a big unresolvable misunderstanding. With the newfound resolve, he opened his orange eyes. And hyper dying will flames materialised on his forehead and arms.

FINAL NOTE: Dio and Giove are Italian words for 'god' and 'Jupiter' respectively. Hence, Dio Giove meant sky god.

Thank you for reading! Feedbacks are highly appreciated. :)