626.bottlenecks.
Rising with the sea at its back, Karatsu Castle was a massive fortress that turned the terrain itself into a weapon.
The waterways of Karatsu Bay flowed around the castle's north and west sides.
Tides rushing from the open sea into the bay collided, forming whirlpools, and those currents scoured the base of the walls, becoming a natural moat.
To lay siege required ships, and to bring ships close meant matching the tides.
To an enemy, it was a wall that never stopped moving.
The land around Karatsu had originally been gentle plains.
To form the castle's base, the ground had been raised in tier upon tier, like steps, and the traces were clear.
Huge retaining walls stood in ranks facing sea and land alike.
Each was built from a mix of black basalt and gray sandstone, balancing strength with resilience.
They rose higher than five jang.
As one moved toward the sannomaru and the main keep, the slope grew steeper and the paths narrower.
The structure was like carving a castle onto the shell of a giant turtle.
From afar, the road from the gate to the keep looked straight and wide.
Up close, it bent in subtle places.
The angles were set so that direct fire and frontal charges were impossible.
At every bend, devices were concealed with care.
Firing lanes ideal for crossfire.
Sudden bottlenecks.
Protrusions from which stones and spears could be dropped.
Small side pavilions where one could take cover.
A road that looked broad had been shaped into a trap.
At the castle's center, the main keep stood at the end of the stepped retaining walls.
It sat atop a rocky back, facing the sea wind and sunlight head-on.
The place held two meanings.
From any direction, it stood in full view.
From the keep, sea, estuary, and plains spread out at a glance.
It was the heart of strategy, and the final point of despair an enemy would face.
Karatsu Castle's distinctive feature was its mixed design.
It combined the moat of a sea castle, the slopes of a mountain fortress, and the interior space of a flatland castle.
The sea served as a moat.
The retaining walls were stacked along steep slopes.
Inside, wide spaces opened like those of a flatland castle.
When a large force advanced, it was met on open ground.
When elites slipped inside, they were caught at the bends of the slopes.
Sea infiltration was locked by the tides.
The word "impregnable" was built into its structure.
Standing on the wide flat ground before the keep, Park Seong-jin looked at the castle and said,
"They put real effort into this."
"Far more than expected."
"A frontal assault would cost dearly."
Song I-jeong chuckled.
"Indeed."
"We're already inside the castle."
Park Seong-jin spoke quietly.
"Since they're trying some petty assassination, we just keep breaking them until they see their limit."
Hearing this, Motonari felt a chill run down his spine.
He read the meaning of standing here now with his whole body.
The final slope leading to the keep was a broad rocky incline, taking the sea wind head-on.
The stonework added to the retaining wall had been deliberately smoothed.
The upward angle was steep.
A slip would send one tumbling all the way down.
When Park Seong-jin stepped forward, the wind whipped fiercely at his clothes.
"Here?" he asked, turning to Motonari behind him.
Motonari shook his head at once.
"Not yet, General. There will be an ambush above."
"How?"
Motonari pointed to both ends of the slope.
"They'll block that end."
"And the exit below, the one we just came up."
He looked to the wall atop the retaining structure.
"Then they'll shoot from above."
"From the gaps in the firing platforms."
"Forward and retreat both cut off, we'll be caught in arrow fire."
Swallowing, he added,
"You can see the archers hiding there."
"They really mean to do it."
Park Seong-jin silently scanned the slope.
It was clearly a killing zone.
"You haven't earned their trust," he said to Motonari.
"That puts you in danger too."
"They've already counted that risk."
Motonari bit his lip.
He knew the smell of that world well.
It was the world of those who had lived with puffed chests as the next great lords.
"…How foolish, the years I lived without knowing this."
The premonition turned into reality at once.
The path ahead closed.
From above, a massive wooden barricade slammed down.
From below, thick log barriers rolled in, sealing the retreat.
"They're here!" Motonari shouted.
At the same time, black shadows flickered in the gaps of the firing platforms and loopholes above.
The air overhead trembled.
The next moment—
Kak. Kak. Kak.
Bowstrings snapped in unison from dozens of platforms.
A rain of arrows rode the wind, pouring down like black rain over the entire slope.
The samurai shouted,
"Fire—!"
"Leave no one alive!"
The arrows plunged straight down, nearly vertical.
They struck with force enough to pierce armor.
From afar, it looked like a monstrous bird beating its wings and scattering scales.
Park Seong-jin did not brace himself.
He stood like the calm center of a storm.
He raised his right hand and lightly swung his blade.
Tang. Tang. Tang. Tang.
At times he flicked them aside with his hand.
At times he guided them off with the scabbard.
At times he deflected them with the tip of his foot.
Invisible currents twisted around him, changing the arrows' paths.
Before they could touch his body, the arrows lost their force and fell.
The warriors behind him felt the protection extend to them as well.
The redirected arrow rain rose back toward the loopholes.
Direct shots no longer held.
The arrows arced high, then fell again—
into the heads, shoulders, backs, and chests of those who had drawn the bows.
Screams erupted beyond the retaining wall.
Motonari swallowed hard.
"…What… is this…"
Park Seong-jin advanced.
Another volley came from above, but he swung his arm once more.
The arrows lifted into the air and poured down onto the flat ground atop the wall.
More screams followed from the firing platforms.
Park Seong-jin did not raise his head.
Wherever he stepped, arrows scraped the ground and snapped.
The wooden barricade blocking the way was a barrier woven from multiple logs.
It would take time to cut through with axes, and even battering rams would need long work.
Park Seong-jin did not draw his blade fully.
With his left hand on the scabbard, he drew the sword only an inch with his right.
He slashed forward once, short and clean.
Kwang.
A roar like an explosion burst out.
The barricade split from the front—cleanly in two.
Wood shards flew everywhere.
The samurai cried out,
"That's impossible—!"
"Is that even human—?!"
As the barricade collapsed, the archers above fell into chaos.
The moment Park Seong-jin's foot touched the stone of the slope, the ground thundered.
His body surged upward like the wind.
The height to the top of the retaining wall was three stories by human measure.
He climbed as if stepping on air.
A shadow fell over the samurai.
Descending through the air, Park Seong-jin drew his sword.
A long, thin streak of light flashed past.
When his foot touched the ground atop the wall, more than ten men collapsed without even setting their stance.
A light sound scattered, like leaves torn by wind.
Park Seong-jin sheathed his sword.
Below, Motonari and the warrior band watched from the slope.
In that moment, the samurai of Karatsu Castle understood:
no device of this castle could stop this one man.
The truth that the castle's structure itself was collapsing before him.
On the path toward the keep, Park Seong-jin glanced once at the pile of bodies, then once at the sea.
He looked up at the keep raised upon the retaining walls.
The road was built to be climbed.
A road meant for ascending steps.