Five days.
Five sunlit cycles within the vast, luminous bubble of Fish-Man Island.
Five days of relative calm, punctuated by the rhythmic, thunderous clashes from the royal training grounds.
For King Neptune, these five days had been a revelation.
Gone was the crushing weight of his grief, the weary resignation that had settled upon him since Otohime's passing.
In its place, a spark had rekindled.
He had found it in the relentless, exhilarating challenge of sparring with Guts, the Devil Swordsman.
Each morning, the moment his royal duties allowed, he would seek out the human, trident in hand.
He felt alive again, his scales tingling with the thrill of battle, the strategic dance of attack and defense.
It was as if he were a young prince once more, roaming the vast, untamed seas without a care for the world, only the wind in his hair and the next horizon to chase.
Of course, the reality was stark. He still had no match against Guts's inexhaustible stamina and utterly inhuman strength.
The sheer, overwhelming power behind the Dragonslayer was a force of nature, a blizzard of steel that never seemed to falter.
Today, as on so many days before, the outcome was inevitable.
Neptune, despite his renewed vigor, found himself pressed back, his trident barely deflecting the monstrous swings.
With a final, blurring movement, the edge of the Dragonslayer, cold and unyielding, came to rest directly against his neck, a hair's breadth from his jugular.
Neptune breathed heavily, his massive chest heaving. A wry, defeated chuckle rumbled deep in his throat. "Forty-three," he gasped, the number thick with a mix of exhaustion and grudging respect.
"For the forty-third time, Devil Swordsman. I admit defeat."
Guts didn't move the sword.
He simply held it there for a moment, his dark, unseeing eyes fixed on the King.
Then, with a practiced motion, he plunged the Dragonslayer point-first into the training ground's solid coral floor.
The massive blade vibrated, humming with latent power.
Guts then turned, lowering himself to the ground, his back resting against the Dragonslayer's broad, black steel, his gaze patient.
He just sat there, waiting.
He knew.
He was waiting for Neptune to say whatever was weighing so heavily on his mind.
Neptune stood there for a long moment, the cool sensation of the Dragonslayer still ghosting on his neck.
He looked at the quiet human before him, a grim, unyielding figure who had unleashed unimaginable horror, yet had been called back by the simple cry of "Father."
The word resonated deeply within him, a king who had lost his queen, now terrified for his youngest daughter.
Hesitation warred with desperation, but finally, a king's resolve, bolstered by a father's fear, won out.
He took a deep breath, his voice hushed, more intimate than any royal decree.
"Devil Swordsman... Guts."
He gripped his trident tightly, its polished surface cool beneath his hand.
"I... I come to you not as a King to a formidable warrior, but as a fellow father."
His gaze was direct, earnest.
"My youngest daughter, Shirahoshi... she lives in fear. Trapped in her chambers for days, terrified of the constant, vile 'gifts' from Vander Decken IX, a deranged pirate who believes her to be his fated bride."
Neptune's voice cracked with a rare, raw pain.
"He hunts her, Guts. My six year old daughter, he desires her for his own. And I... I am powerless to stop him without risking her life, without bringing even greater tragedy upon her head."
He looked at Guts, then at the Dragonslayer plunged into the ground, then back at Guts's unseeing eyes.
"You... you commanded a mighty Sea King. A creature of the deepest ocean, who listened to your every word. I saw it. I saw how he protected your daughter for you."
His voice lowered to a desperate plea.
"I... I ask you, Devil Swordsman. As one father to another. Lend me that power. Help me to free my daughter from Decken's hand."
Guts remained silent, his expression unchanging.
He listened to the King's every word, his face a mask.
After a moment, he slowly, deliberately, shook his head.
"Hmph." Guts grunted, his voice a low, rough rumble.
He leaned back against the Dragonslayer, settling more comfortably.
"That thing?"
He gestured vaguely towards the palace exterior, indicating Gargar.
"That's the kid's pet."
He paused, a hint of something resembling amusement in his tone.
"You need to talk to the kid. She's the one who calls the shots for that thing."
King Neptune blinked, his massive jaw dropping slightly.
His heart, brimming with a father's plea, skipped a beat. The fate of his daughter rested on... "the kid"? On Robin?
Five days had passed since the intense welcoming of Fish-Man Island.
For Guts and Robin, these days were a quiet rhythm of exploration and contemplation. They wandered through the luminous coral cities, observed the bustling marketplaces, and delved into the ancient, silent libraries of the palace, seeking the elusive "something not yet clear" that Robin sought.
The clues remained hidden, but their bond deepened with every shared discovery, every shared silence.
That evening, as the bioluminescent glow of the Ryugu Palace began to deepen, King Neptune, a figure of profound sorrow and newfound hope, gently knocked on Robin's chambers.
"Young lady," his booming voice softened to an inviting tone, "would you care to join me in the Royal Garden?"
Robin, intrigued, accepted.
The garden was a breathtaking sanctuary beneath the sea.
Fields of shimmering, delicate Amber coral roses pulsed with an inner light, their petals unfolding in slow motion, painting the water with ethereal hues.
Neptune sat on a large, smooth rock, his gaze sweeping over the beauty around them.
"My beloved wife, Otohime."
Neptune began, his voice thick with a tenderness that bordered on reverence.
"She adored these coral roses. She planted every single one herself, tending to them with a love as deep as the ocean. After her passing... this place,"
His voice hitched slightly.
"This place is my only comfort. Her presence feels strongest here."
Robin listened quietly, her eyes taking in the profound beauty and the King's raw vulnerability.
She understood.
She knew the crushing weight of loss, the ghost of loved ones clinging to places of comfort.
After a long moment, Neptune turned to her, his immense eyes filled with an appeal that was both royal and deeply paternal. He recounted the agonizing ordeal of his daughter, Shirahoshi, imprisoned by fear, haunted by the malicious "gifts" of Vander Decken IX.
He spoke of his own powerlessness, the agonizing dilemma of a father unable to truly protect his child.
"I have already spoken to the Devil Swordsman," he concluded, his gaze earnest.
"He said... he said I needed to speak with you."
Robin listened, her expression calm, yet a profound empathy bloomed within her.
She felt it, this same agonizing feeling that resonated within Guts, the familiar ache of a father who would do anything for their child.
She saw it in Guts every day – his constant battle, how he kept breaking apart and reconstructing himself, body and soul, repeatedly, just to keep her safe.
The monstrous visions she had glimpsed from him, the fear for that beautiful, wheat-haired woman, and the horrifying overlap with herself – it was all driven by this very love.
This was the burden Guts carried for her, and now, she saw it in Neptune for his own daughter.
Without hesitation, her resolve firm, Robin looked at the King.
"I agree to help, Your Majesty."
The next morning, the grand banquet hall was bathed in the soft, diffused light filtering through the palace's high, crystalline domes.
Guts was already at the long, ornate table, a massive platter of roasted deep-sea boar already half-empty beside him, his mug clinking against the table as he reached for more.
Robin, nursing a cup of fragrant kelp tea, decided to address the matter directly.
"Father," she began, her voice calm.
"Last night, King Neptune spoke to me about his daughter, Shirahoshi, and the pirate Vander Decken."
She watched his unreadable face.
"He asked for our help. I told him... I agreed."
Guts paused, his mug halfway to his lips.
He lowered it slowly, then simply gave a single, distinct nod of understanding.
No questions, no arguments.
Robin had decided.
That was all that mattered.
That afternoon, Robin walked to the grand pier that stretched into the open waters of the bubble.
Gargar, the enormous shark-kraken, was there, his massive form a comforting presence.
He let out a soft rumble of recognition as Robin approached, his cheerful eyes blinking slowly.
"Gargar," Robin said, her voice gentle.
"I need your help with something important."
She explained, in simple terms, the plight of King Neptune and the threat of Vander Decken. Gargar listened, his vast body shifting restlessly.
When she finished, the colossal creature gave an enthusiastic, booming rumble that vibrated through the water, then saluted with a huge, suckered tentacle, a movement that was perhaps too eager, knocking over a nearby curious fish-man and mermaids.
He was clearly ready for action.
Robin then closed her eyes, extending her senses. Her "Whisperer" ability, honed by years of connecting with the world's hidden truths, unfurled.
She reached out, not to the massive Sea Kings this time, but to the countless small fish in the surrounding area.
She communicated with them, a silent request rippling through the currents: Locate Vander Decken.
Tell me where he is.
It wasn't even an hour later.
The scattered, glittering fish returned, a swirling school of living intelligence, their collective voices whispering a detailed map of the ocean currents, a specific bearing, and a precise depth.
Decken's location was pinpointed.
Moments later, the waters of Fish-Man Island parted for an unlikely duo.
Gargar dashed through the currents with a speed that belied his gargantuan size, a living torpedo aimed at his target.
And on his broad, unyielding back, stood Guts.
The "Devil Swordsman" was fully enveloped in his demonic Berserker Armor, its jagged, black plates shimmering malevolently even in the ambient light of the deep.
The immense pressure of the ocean, the resistance of the water – it affected him not much, his unholy strength and the armor's terrifying properties rendering him an unstoppable, inhuman force even in this alien environment.
He was the spearhead of a father's promise, delivered by a daughter's will.
Far away, in the murky, depths of the sea, on a dilapidated, barnacle-encrusted ship, Vander Decken IX sat in his captain's chambers.
He was a grotesque, bulbous figure, holding a delicate, framed photograph of the six year old beautiful Shirahoshi.
He was sipping wine, a smug, possessive smile on his face, lost in his twisted fantasies.
He was utterly unaware of the disaster that was about to befall him.
He felt a sudden, seismic jolt. His wine sloshed over his hand.
His ship, his beloved Noah, suddenly groaned, a terrifying sound of tearing metal and splintering wood.
Before Decken could even register the impossible impact, before he could gather his thoughts, before his brain could even process the sensation of crushing steel and the monstrous shadow that fell over him...
SHLICK!
The Dragonslayer, massive and unforgiving, descended with the force of a falling star, splitting him apart from head to grotesque toe.
There was no time for a scream, no time for a final thought.
Just the wet, final sound of a life extinguished, obliterated by the force of pure, uncompromising retribution.