After obtaining the Op-Op Fruit, Noah and his companions continued their submerged voyage through the North Blue aboard the Nautilus.
Because of the Arctic Circle and the Arctic ice cap, the northern reaches of the North Blue were almost entirely covered in ice and snow, with a climate much like that of Drum Island in the Drum Kingdom.
The Nautilus did not have a smooth passage beneath the waves, as there were too many underwater icebergs and hidden currents in these waters.
Beyond Labrador Island, there were no more World Government Affiliated Nations to the north.
The land in the Arctic region was barren, and its small nations were mostly made up of fishing and hunting tribes. Among them, the Amoski People were a relatively well-known group.
Noah took Luo and Ray to visit several small Amoski tribes, then turned southwest once more.
Half a month later.
They reached Swallow Island, where they found Bepo, a young member of the Mink Tribe who had ended up stranded there, along with several other orphans. Among them were Penguin and Shachi, who would later join the Heart Pirates.
Over the past month or so, Luo had also become increasingly proficient in using the Op-Op Fruit's abilities.
With Noah's guidance in particular, Luo would develop the Op-Op Fruit faster and more thoroughly than he had in the original timeline.
After all, the concept behind the Op-Op Fruit was surgery, or rather, concepts drawn from surgical medicine. In that respect, Noah could give Luo a wealth of ideas to draw on.
For example, there were avenues such as X-rays, ultrasound, nuclear magnetic resonance, proton and heavy-ion radiation, and gamma rays. Without exposure to these medical technologies, Luo would have had a hard time developing related derivative abilities.
But with Noah's pointers, the outcome was different.
Although Luo's stamina was not yet sufficient to support the use of the "X-ray," "gamma ray," and "proton and heavy-ion" derivative abilities, he could already make basic use of the "nuclear magnetic resonance" and "ultrasound" types.
On the northern wasteland of Swallow Island.
Luo used ultrasound together with his newly awakened Observation Haki to dodge Ray's attacks swiftly.
Even though the Op-Op Fruit had Room, a special spatial ability that allowed Luo to move through space within a certain range, he still could not dodge every one of Ray's attacks.
Panting, Luo was well aware of his weakness. Stamina was the foundation of a fruit's powers; if it was insufficient, even an extremely powerful Devil Fruit ability would perform terribly.
This could be seen in how Ace and Sabo each used the Flame-Flame Fruit.
At the same time, the gap between their levels of Observation Haki was another reason Luo could not avoid Ray's attacks.
Not far away, Bepo, Penguin, Shachi, and the others were also training their physical skills.
Noah, meanwhile, was underground on Swallow Island, using the caverns Ray had dug over the past few days to set up a temporary base.
Although the vast majority of the Noah Family's strength was in the East Blue, that did not mean they would abandon the other three seas.
Noah and Jay were currently testing a special device together.
On top of the rocky hill above the caverns, more than a dozen "dead trees" grew between the cracks in the stone. A closer look would reveal that their surfaces were densely covered in tiny black crystals.
These were "modified graphene crystals" that Jay had created using his ability. They absorbed electromagnetic signals from their surroundings and transmitted the received signals into the underground caverns.
Then, several specially bred Den Den Mushi decoded the information.
In fact, to breed these intelligence-stealing Den Den Mushi specifically for decoding, the Noah Family had sacrificed hundreds of Den Den Mushi and used IQ components and a considerable amount of life force before successfully breeding a dozen or so of them.
The first telephone eavesdropping station had been established on Sikasis Island.
Swallow Island was the second.
Once the lines were connected, Jay and several winged people who had joined the Noah Family began the demanding tests.
This intelligence-stealing work was not conducted blindly; it required specific planning and techniques.
It could be divided among six offices: number identification, relationship mapping, key-person classification, dedicated monitoring, intelligence analysis, and overall coordination.
The eavesdropping station would certainly not focus its attention on Den Den Mushi communications between ordinary factions. The forces it truly needed to monitor closely were the World Government, Cipher Pol, and the Marines, or regional powers, the Revolutionary Army, and major pirates.
In the North Blue, for example, the first forces Noah selected for close attention were the Vinsmoke Family, the Donquixote Family, and Marine Vice Admiral Tsuru.
As for how to identify these forces' telephone numbers,
the answer was keyword monitoring.
For the Donquixote Family, for example, based on the information Noah had, whenever the other party mentioned terms such as "Doffy," "young master," "Donquixote," "Pica," "Diamante," or "Trebol" during a call, the recorder would flag the number for preliminary identification and continue monitoring it for a time, until its owner's identity could be confirmed.
Although anti-eavesdropping Den Den Mushi existed in the pirate world, they were not widely used, mainly because of their production volume and the government's strict controls.
Moreover, many factions rarely used anti-eavesdropping Den Den Mushi in their everyday calls.
That gave the Noah Family an opportunity to listen in on their calls.
Sure enough, on the morning of the fourth day after the Swallow Island eavesdropping station went into operation, it intercepted a Den Den Mushi signal from the Marines.
At first, the recorder had not noticed anything amiss.
Only when the conversation contained information about Vice Admiral Tsuru's whereabouts and mentioned terms such as "young master" and "family" did the recorder pay attention.
As they continued monitoring the two numbers, the Den Den Mushi numbers of the entire Donquixote Family were quickly identified, along with those of some underground forces in the North Blue.
Doflamingo, who was currently evading Vice Admiral Tsuru's pursuit, had no idea his telephone number had been identified.
The eavesdropping station recorded some of the valuable intelligence.
As Noah browsed through it, he suddenly came across a very valuable piece of information.
[Recorded: Sea Circle Calendar 1505.07.22. Call participants: Doflamingo and Diamante Call record: A girl suspected of being a Devil Fruit User was found in the Angubo Archipelago. Her ability may be that of the Snow-Snow Fruit...]
Are they the sisters Monet and Sugar? Noah glanced at a map of the North Blue and found that the Angubo Archipelago was not too far from Swallow Island, only about 976 kilometers away.
He then recalled what he knew about the sisters Monet and Sugar.
It was 1505, so Monet should have been thirteen and Sugar five.
Monet had eaten the Snow-Snow Fruit by this point, while Sugar probably had not, because the Hobby-Hobby Fruit had one particular trait: the moment someone ate it, their body stopped aging.
In the original timeline, Sugar's physical age was ten.
In other words, Sugar should have eaten the Hobby-Hobby Fruit when she was ten.
Although Sugar had not eaten the Hobby-Hobby Fruit, Noah had no intention of leaving the two of them to Doflamingo.
Doflamingo and his family members were currently evading Tsuru's pursuit and had no time to search for the sisters Monet and Sugar, so Noah could seize the opportunity.
Noah quickly ordered Ray and the others to set sail.
Soon, the Nautilus was heading toward the Angubo Archipelago at full speed.