Sky Island...
An explosive shockwave erupted across the ocean as massive tidal waves surged into the sky. Riding the vertical ocean blast, the Sunagakure Pirates and the Shukaku hurtled straight toward the heavens, transforming into a soaring water pillar beneath a dense blanket of storm clouds.
"This defies common sense on every level..."
Shiraishi dismissed his crew's complaints with a dry chuckle: "There are plenty of things in this world that defy common sense—no need to get worked up over it!"
"Engage the dual-wing air propulsion!"
Specialized air-spiral turbines extended from both sides of the Shukaku's hull. Harnessing the rising thermal updrafts, the warship hovered upward with the wind, spinning gently in an ascending spiral along the vortex.
"So the rumors were real after all! To think the secret to reaching Sky Island was using a marine geyser to rocket into the sky... That means the story about the City of Gold... Gods above, we're going to be rich!"
It wasn't just Ace who was stunned; even a seasoned navigator like Moyard gaped in disbelief at the sight unfolding before their eyes. Had Shiraishi not insisted on this insane method, none of them would have ever imagined ascending this way.
"First, head toward the entry edge of the White Sea..."
At the pinnacle of the colossal water column lay a vast ocean composed entirely of clouds. The Shukaku settled smoothly onto the White Sea, drifting along the cloud currents while Shiraishi continually monitored the local atmospheric readings.
Moyard and several other crew members looked visibly pale. The drastic drop in air pressure at high altitude was taking a toll on their bodies, prompting Shiraishi to hand out a freshly prepared tonic for everyone to drink.
"The Sea Kings in these cloud waters are significantly larger than normal ones. They've evolved larger bodies with much lighter mass to stay afloat in the high-altitude cloud ocean..."
In short, they turned themselves into living balloons...
Intrigued by the explanation, Ace was the first to act when a massive shadow bellowed outside. Unleashing a concentrated spear of flame, he blasted a giant hole through the cloud sea.
A short moment later, the bloated carcass of a perforated Sky Sea King floated to the surface, serving as fresh rations for the crew.
"Not bad at all..."
After some simple preparation, the flavor of the Sky Sea King proved surprisingly superior to the fish found in the Blue Sea below.
"Now that we've reached Sky Island, what's your next move?"
As Uchiha Madara adapted to the thin air pressure, he adjusted the sheath of a new blade resting at his waist—the Kaishūtō (Ring-Staff Sword), one of the 21 Great Grade Swords (Ō Wazamono).
Shiraishi had commissioned the Germa Kingdom to track it down. While it wasn't one of the 12 Supreme Grade Swords, it remained an exceptional weapon.
Also known as a Nodachi, the Kaishūtō possessed a straight, uncurled blade crafted by the legendary Bizen smith Kunimune.
Historically favored by the Uesugi Daimyo in the Land of Wano, its hilt and scabbard were carved from a single 5-foot piece of natural timber, giving it its iconic name.
It had been passed down through generations of the Uesugi family until internal turmoil decades ago led to their downfall, causing the blade to drift overseas into the underworld market—eventually ending up in Madara's hands.
Relying solely on his gunbai war-fan and scythe offered surprising tactical utility, but against a master swordsman like Patrick Redfield, Madara had been forced to recognize the limitations of his weaponry in pure blade clashes.
"We head to Birka to seize the Logia Rumble-Rumble Fruit (Goro Goro no Mi). Once equipped, we mobilize for a full assault on Upper Yard."
"Sky Island is the ideal staging ground to build our territorial foundation."
At present, the military strength of the Marines and the World Government had not eroded to the degree it would decades later. As a result, even in the New World, few pirate crews blatantly staked out sovereign territory the way the future Four Emperors (Yonko) would.
Therefore, Shiraishi set his sights on Sky Island in the first half of the Grand Line. Given its isolation from the Blue Sea—with Gol D. Roger's crew being the only notable visitors—Shiraishi planned a preemptive strike to claim the entire region as his domain.
To subjugate Sky Island, Shiraishi adopted Enel's playbook: start at Birka, assemble a divine army, and launch a counter-offensive against Upper Yard.
Sky Island's so-called "God" was essentially an administrator chosen through a council of multiple sky islands, though the faction occupying Upper Yard—the sacred land fallen from the heavens—held the ultimate authority.
The High Priests who emerged later clearly hailed from factions outside Upper Yard and Angel Island.
"Has everyone adapted to the altitude?"
After drinking the medicinal brew, most crew members stabilized their physical condition. Still, Shiraishi felt shorthanded; his current crew size was far too small to govern the region on its own.
To maintain long-term control over Sky Island, he needed to govern the locals using local assets...
Birka was not only the key to securing the Rumble-Rumble Fruit; it was the cornerstone of Shiraishi's entire territorial strategy.
As the second-largest sky island in the White Sea after Angel Island, Birka's inhabitants lived a peaceful, detached existence. Unlike Upper Yard—where the Shandians waged relentless war every year to reclaim their ancestral land—Birka was a quiet and idyllic haven.
Until one fateful day...
A colossal warship glided silently across the cloud sea in the distance...
The local islanders gathered on the shore, watching the approaching Shukaku with intense curiosity. However, the moment they caught sight of the dense rows of heavy cannons lining its hull, their expressions turned to terror.
"What is that?!"
"They look like people from the Blue Sea...!"
Since Roger's crew had never visited Birka, the local inhabitants were deeply suspicious of outsiders. Among them, the resident High Priest watched the approaching vessel with a grim, stern gaze.
The local High Priest of Birka was named Hakufukushan, an old-guard ruler. Unlike the complacent "God" residing in Upper Yard, Hakufukushan was an ambitious and proactive leader.
The military force and priests he had amassed on Birka were no smaller than those of Upper Yard. Yet over the years, Birka's priest faction had deliberately refrained from involving itself in the endless war between the Shandians and Upper Yard's Angels.
While Shiraishi couldn't speak for every resident of Birka, analyzing his knowledge of Enel's future priestly army made one thing clear: when Upper Yard's native priests were ousted, Enel easily recruited a cohort of Birkan priests to govern Sky Island. This proved that the high-ranking factions among the Angel race were far from unified.
Even after Enel eventually destroyed Birka, those trial priests remained fiercely loyal to him, further proving the raw ambition harbored by Birka's elite.
Exploiting this internal divide was precisely why Shiraishi made Birka his first stop, rather than heading directly to Upper Yard in the central sector...
Seeing no word arrive from the sky checkpoint, Hakufukushan knew these outsiders hadn't come in peace!
"Prepare for battle!"
Though confused as to why Blue Sea invaders would appear at Birka rather than Upper Yard—where all the gold was located—Hakufukushan wasted no time. Winged Angel shock-troops assembled in rapid formation, leveling their weapons directly at the Sunagakure Pirates.