With a soft burst of air rushing in, the bubble coating around the Twin Goddesses swelled as it passed through the entrance of Fish-Man Island and entered the open sea.
Under Den's control, the ship slowly began to rise.
On the deck of the Twin Goddesses, the girls led by Flare, along with the Kuro Brothers, leaned excitedly over the edge of the deck to look down.
Below them, the enormous Fish-Man Island gradually grew smaller and smaller. From this height, scenery they had never been able to see during the past few days slowly revealed itself.
"This is amazing. It already felt beautiful while we were on the island, but looking at it from above makes it even more incredible."
"It looks just like a crystal ball!"
Baby-5 happily lay on the deck railing as well, swinging her short legs while speaking.
From above, the entire Fish-Man Island truly looked like a toy sealed inside a crystal ball.
Especially under the dazzling glow of the Sunlight Tree Eve, the bubble surrounding Fish-Man Island shone brilliantly, radiating vibrant, colorful light.
However, as the Twin Goddesses continued to rise, the light emitted by the Sunlight Tree Eve gradually dimmed.
It seemed that only the roots of the Sunlight Tree Eve were capable of producing light.
Flare looked around, then raised her head to observe the surroundings.
When they first arrived at Fish-Man Island, the light had been so bright that it was difficult to see the environment clearly. Now, with the softer glow around them, the entire seabed became clearly visible at a glance.
"There are this many roots from the Sunlight Tree Eve? I thought there were only two."
Across the vast seabed, the roots of the Sunlight Tree Eve stretched deep into countless areas, glowing faintly as they illuminated the entire underwater world.
Among them, the three massive roots surrounding Fish-Man Island stood out the most. They were incredibly straight and arranged in a triangular formation, enclosing the island within their protection.
Looking at the roots, Flare said thoughtfully,
"The Sunlight Tree Eve looks pretty similar to the red trees on the Sabaody Archipelago."
Hearing this, Den, acting as their guide, began explaining.
"That's not entirely wrong. In fact, the red trees on the Sabaody Archipelago can be considered branches that split off from the Sunlight Tree Eve."
"Huh? Really?"
"Mm."
Doing his job as a guide perfectly, Den pointed toward Fish-Man Island beneath them.
"You can see it from here. The bubble surrounding Fish-Man Island is actually made up of two layers."
"Yeah."
Everyone nodded. They had already noticed this when they first entered Fish-Man Island.
Aside from the fact that the entire island was formed by two bubbles, one large and one small, which enclosed Fish-Man Island and Ryugu Palace respectively, each of those bubbles was itself made of two layers.
In simple terms, it was a large bubble surrounding a smaller bubble.
The inner bubble contained the actual Fish-Man Island and Ryugu Palace, while the outer bubble functioned more like a protective barrier.
Between the two layers were both air and seawater.
"Actually, out of these two layers, only the outer one is made from the resin of the Sunlight Tree Eve. The inner one isn't."
"Huh?"
"Why not use the Sunlight Tree Eve resin for both?"
Everyone asked curiously.
Den pointed at the outer bubble as he explained,
"The reason is simple. The resin secreted by the Sunlight Tree Eve has a very unique property. When you entered Fish-Man Island earlier, someone must have mentioned this. If you try to enter the island without going through the official entrance, the coating bubble applied at the Sabaody Archipelago will be absorbed by the outer layer surrounding Fish-Man Island."
The group thought back for a moment and nodded.
"That Shark Fish-Man did mention that."
"That's exactly it. The resin of the Sunlight Tree Eve has a very unique property. You could think of it as fusion and absorption. To put it simply, bubbles formed from the resin of the Sunlight Tree Eve will automatically merge with and absorb other bubbles. Let me show you, and it will be easier to understand."
As he spoke, Den took out a piece of bubble coral from his pocket. With a light press, a bubble instantly formed and wrapped around his entire body.
Then Den jumped forward and passed straight through the bubble coating surrounding the Twin Goddesses, entering the sea.
However, the bubble around his body did not burst, and the bubble surrounding the Twin Goddesses remained completely intact.
Den then removed the bubble from around himself and held the now empty bubble in his hands as he swam toward the outer bubble surrounding Fish-Man Island.
Then an astonishing scene unfolded.
The bubble created by the bubble coral instantly fused into the outer bubble the moment it touched it.
At that point everyone finally understood. Den swam back to the ship, shaking the seawater off his body as he explained.
"That's basically how it works. Not only the bubbles produced by our Fish-Man Island's bubble coral, but also the bubbles made from the red tree resin on the Sabaody Archipelago behave the same way. Also, you've seen the three roots surrounding Fish-Man Island, right?"
"Unlike the bubbles on the Sabaody Archipelago, which release resin through respiration and allow it to float into the air and disperse, there's no air deep in the ocean. Because of that, the resin secreted by the roots of the Sunlight Tree Eve can only flow downward along the trunk. Eventually, it merges into the outer bubble surrounding Fish-Man Island. Over hundreds and thousands of years, this outer bubble has become extremely strong."
"Strong?"
Everyone found it hard to connect that word with a bubble. After all, it just looked like a giant air bubble.
Seeing their confusion, Den thought for a moment before continuing.
"Let me put it another way. On land, you've probably heard of a material called rubber."
Everyone nodded.
"You can think of the outer bubble surrounding Fish-Man Island as a kind of transparent rubber with extremely powerful elasticity. What that means is that this bubble can stretch and deform in unbelievable ways, just like rubber that can be endlessly pulled and reshaped. Unless it reaches its absolute limit, this bubble can compress and stretch freely. Even cannons or Sea Kings can't break through it."
"That's amazing!"
"So it's like a balloon!"
Everyone felt like they had learned a lot.
"Den-san really knows a lot!"
Seeing this, Tiger added with a smile,
"Besides being a shipwright, Den is also a very famous scholar here on Fish-Man Island."
Everyone's eyes immediately lit up. Ayala in particular looked like she wanted to run up and start asking questions right away.
Den continued his explanation enthusiastically and pointed toward a massive structure attached to a distant tree root.
"Do you see that? That's the air reservoir."
"The air reservoir?"
"That's right. It's built on the tree roots and stores the air produced by the Sunlight Tree Eve. The stored air is then sent down to Fish-Man Island to regulate the island's atmosphere."
"That's incredible..."
And so the journey continued with Den explaining various things while everyone listened with great interest, occasionally responding with surprised reactions.
But at that moment, Tiger suddenly noticed that his captain's expression seemed strange.
Yemu's eyes were wide open, as if he had just realized something unbelievable. Yet at the same time, he frowned slightly, looking uncertain, almost as if he doubted his own thoughts.
Curious, Tiger asked,
"Captain, what's wrong? Is something bothering you?"
At that moment, Yemu felt his thoughts were in complete chaos. However, one particular point from Den's explanation had stuck firmly in his mind like a nail, refusing to move.
With a complicated expression, Yemu finally asked,
"Den-san... did you just say rubber?"