At a depth of 6,000 meters beneath the sea...
Five enormous sea beasts drifted in the dark waters, and atop each of their heads stood a burly fishman.
At the front was the fishman known as Jinbe. The other four were Aladdin and Arlong from Fish-Man District, along with Whale Fish-Man and Shark Fish-Man of the Neptune Kingdom's army.
As more and more pirates poured into the seas, Fish-Man Island had taken a heavy blow.
Countless powerful pirate crews had landed on the island, and with them came an endless stream of human traffickers.
Fish-Man Island had entered its most chaotic era.
To protect their homeland, fishmen and mermen—who rarely saw eye to eye—had joined forces.
Today, they had received news that a mermaid had been captured by traffickers, and they had chased the culprits all the way here from Fish-Man Island.
But...
"Why? Why did you stop chasing them?!"
Seeing the others halt, Jinbe roared in fury.
"Jinbe, calm down. We can't catch up anymore. Those humans have already escaped into the Deep Trench."
The one who spoke was the Whale Fish-Man of the Neptune Kingdom's army—fishman with an especially round belly that made his stout figure even more pronounced.
He wasn't speaking without reason. The immense downward currents of the Deep Trench made it difficult even for Sea Kings to swim upward through it. Yet human ships, relying on Kuuigosu's buoyancy, were far less affected.
Living creatures had to expend strength to swim against the current. Ships, on the other hand, only needed to ride the ocean's powerful buoyant force.
Jinbe understood that perfectly well.
But even so, he didn't want to give up.
"If you won't chase them, then I'll go alone!"
"Forget it, Jinbe!"
This time it was Aladdin who grabbed him, shaking his head unwillingly.
"If you go any higher and get too close to the surface, what if you run into those greedy humans—"
Before he could finish, Arlong, who had been glaring angrily into the dark waters above, suddenly froze.
"Hey, Jinbe... look. Isn't that—"
Everyone's attention snapped upward.
Within the raging current, the shattered remains of a ship were being swept downward.
The sight was painfully familiar.
It was the traffickers' ship they had been pursuing.
All of them stood stunned.
"W-What happened here?!"
The Whale Fish-Man asked, his face filled with shock and confusion.
"Could it be... the coating bubble burst...?"
The Shark Fish-Man ventured hesitantly.
Only Jinbe kept his eyes fixed on the wreckage. His voice tightened as he spoke.
"No... Those marks are too clean."
"That was cut by a human swordsman."
"A... a human swordsman's slash..."
The fishmen's expressions changed instantly. Their pupils contracted as tension filled their eyes.
"Then that means... human pirates..."
Over the past few months, the terrifying human pirates who had set foot on Fish-Man Island had left a deep mark on everyone there—one edged with fear.
Especially that swordsman called Mihawk. His blade had been unforgettable.
As if in answer to their words, a massive pirate ship slowly entered the vision of every fishman and mermaid present. Its looming silhouette pressed down on them like a shadow, tightening every nerve.
And just as unease spread through the group, a voice suddenly echoed through the calm, endless depths of the sea.
"Jinbe, Aladdin, Arlong… you've all grown up!"
In that instant, the expressions on Jinbe, Aladdin, and Arlong's faces shifted from tension and shock to disbelief, and finally, tears streamed uncontrollably from their eyes.
"T… Tiger-aniki!!!"
As if answering their cries, Tiger's broad figure appeared at the bow of the ship, his face filled with relief and pride as he looked at his younger brothers.
"Jinbe, Aladdin, Arlong… and Fish-Man Island."
"I'm back!!!"
...
Ten thousand meters beneath the sea lay a place known as the Sea Abyss.
Though it was the ocean floor, sunlight shone brightly.
Between the massive roots of Sunlight Tree Eve floated two enormous bubbles, one large and one small, each enclosing an island.
This was Fish-Man Island. The larger island was home to ordinary fishmen and mermaids, while the smaller one housed the royal palace of Fish-Man Island, also known as Ryugu Palace.
It was the only place on the seafloor where air existed, allowing humans to survive. Everywhere else was filled with seawater, dazzling light, and schools of fish of every size.
The Twin Goddesses sailed steadily forward, heading toward Fish-Man Island.
Around it swam five colossal sea beasts, as huge as Sea Kings, guarding the ship on all sides as they advanced.
At the front, atop the head of the lion-shaped sea beast, Tiger stood with Jinbe, Aladdin, and Arlong at his side. His eyes were unfocused as he took in the familiar sights before him. Feeling the seawater brush against his body, his eyes quickly filled with tears, and he broke down, sobbing openly.
"I'm finally back… Fish-Man Island… my home!"
"Ahhh…!"
Jinbe, Aladdin, and Arlong didn't think much of it, assuming their big brother was simply overwhelmed after returning to his homeland.
Only Yemu, standing on the deck, truly understood what Tiger was feeling at that moment.
"It seems we need to fulfill Tiger's dream as soon as possible. Otherwise, he may never be able to let go of the burden in his heart."
Beside him, Flare pointed curiously at the massive roots.
"So this is the Sunlight Tree Eve you mentioned? I thought it was the Yarukiman Mangrove."
"It's different," Yemu explained.
"We're directly beneath the Holy Land Mary Geoise now, not at the Sabaody Archipelago."
"Oh… Still, it's incredible that a tree like this can absorb sunlight."
The Shark Fish-Man of the Neptune Kingdom's army, who had accompanied them, quickly added with a polite tone,
"The roots of Sunlight Tree Eve transmit sunlight. The top of the tree absorbs sunlight from the surface world, and it's carried down through the roots to Fish-Man Island. Our island relies on Sunlight Tree Eve to receive sunlight."
Flare blinked with curiosity.
"Then does that mean the top of Sunlight Tree Eve is in the Holy Land Mary Geoise?"
The Shark Fish-Man froze slightly, looking awkward.
"I'm sorry… we don't know. We've never been to the surface…"
"I-I'm sorry… I forgot…"
She apologized hurriedly.
"It's alright," he continued politely. "You are Tiger-san's companions, and you saved Loralei. You're friends of Fish-Man Island. If King Neptune and Queen Otohime knew, they would certainly welcome you and express their gratitude."
As he finished speaking, everyone turned to look behind them.
There stood a beautiful blue-haired mermaid, clutching Erik's hand tightly as she stayed close to him.
Ayala, his younger sister, stared at her brother with a particularly strange expression.
"Don't tell me I'm about to get a mermaid sister-in-law?"
Erik's face immediately turned red with embarrassment. He had intended to ruthlessly shake her off, but seeing the pitiful look on the young mermaid's face, he simply couldn't bring himself to do it.
Fortunately, everyone soon looked away.
"So how do we enter? Do we just sail straight in?" someone asked.
The Shark Fish-Man immediately shook his head.
"No, you mustn't. That would be extremely dangerous. The density of the bubble surrounding Fish-Man Island is different from the coating on your ship. If you rush in directly, the bubble around your ship will be stripped away, and the entire vessel will fall into the seawater. You have to pass through the official entrance and have your ship recoated there…"
But just as Shark Fish-Man finished speaking, under everyone's watchful eyes, a pirate ship suddenly burst straight out of the bubble, charging recklessly forward before drifting upward toward the distant sky…