Doflamingo wasn't aware of the specifics regarding Vergo's situation, but he trusted Vergo wouldn't disappoint him. Just as Vergo trusted Doflamingo, Doflamingo trusted Vergo implicitly.
Rosinante had now been with the Family for a month. During this time, he'd finally confirmed that Vergo, whom he remembered from childhood, was nowhere to be seen. He had asked Doflamingo about it, only to be told Vergo was away on a mission. This explanation planted a seed of doubt in Rosinante's mind, making him determined to find out what Vergo was really doing. However, the thought of Vergo infiltrating the Marines as an undercover agent never crossed his mind; after all, for a pirate, that would be walking willingly into the lion's den!
In his month within the Donquixote Family, Rosinante had managed to get along reasonably well with the others. Still, under the guise of his established dislike for children, he persisted in trying to "bully" Robin, hoping to drive her away. Unfortunately for him, Robin's own skills had progressed significantly, making her far from an easy target. Rosinante, needing to maintain his cover, couldn't risk revealing any of the techniques the Marines had taught him. Consequently, the dynamic often reversed, with Robin seemingly bullying him. Despite this, Rosinante didn't give up his objective; he was determined to see this through with Robin.
Clever Robin had known from the start that this Rosinante fellow wasn't truly one of them. Now that he'd set his sights on her, the calculating side of Robin saw an opportunity. She had the perfect excuse to "educate" Rosinante, and so, a subtle battle began between the two, waged both openly and in the shadows.
Doflamingo watched Rosinante's clumsy attempts to scare Robin away, feigning ignorance. He found his brother's clown-like performance rather amusing. In the original timeline, Rosinante had similarly bullied nearly all hundred children selected by the Donquixote Family, managing to drive away everyone except Baby-5 and Buffalo, who simply wouldn't leave no matter what. How laughable! Rosinante, the great philanthropist, deluded himself into thinking he was doing what was best for those children. But in this wretched world, could those kids he'd chased away truly survive and thrive? Most likely, the majority ended up as corpses discarded in the wilderness or became street urchins, resorting to petty crime and worse just to survive. At least within the Donquixote Family, they had a better chance than out there! They could live with a semblance of dignity, like actual human beings!
To Doflamingo, Rosinante's self-proclaimed compassion was pathetic. Trying to decide others' fates without the power to control anything! Assuming that what he thought was good for others was inherently right! Undeniably, Rosinante was kind, but was his kindness truly unconditional? Before hearing that Law's name contained the initial 'D,' would he have truly gone to such lengths, risking everything, to cure him? Wasn't it only because he saw no hope, lacked the power to stop Doflamingo himself, and latched onto the mystique of the "Natural Enemy of the Gods" that he pinned all his hopes on Law, wishing Law could fulfill his own desires?
In reality, Rosinante was selfish too. He was simply selfish in believing that everything he did was just and good! That's perfectly normal; everyone is selfish. Yet, those who stand on the moral high ground rarely admit their own selfishness. In Rosinante's eyes, everything Doflamingo did was wrong. But did he truly understand anything about what Doflamingo had done, or why?
There's no such thing as absolute justice or kindness. There's only the rule of the strong. Only the victors get to write the definition of justice! The mercy of the strong is the greatest kindness the weak can hope for!
His actions were pure clownery. Rosinante behaved exactly as he had in the original timeline, utterly predictable. Doflamingo had no interest in dealing with him for now; let him bounce around uselessly. After all, Doflamingo saw everything Rosinante did. Even his communications with Sengoku were being monitored flawlessly by Ibes.
Setting Rosinante aside, Doflamingo had recently been struck by a new idea for developing his Rumble-Rumble Fruit powers. He was just about to conduct an experiment with Robin and Ibes.
The inspiration came from Ibes obtaining the Zoan Type: Ox-Ox Fruit, Model: Den Den Mushi. If two Den Den Mushi could communicate using biological electrical waves, could Doflamingo simulate those waves to essentially transmit himself?
Once the idea took root in Doflamingo's mind, it became an obsession. If he could achieve transmission via electrical waves, then wherever a Family member was located with a Den Den Mushi for contact, Doflamingo could instantly appear by their side via wave transmission. Even Kizaru, known for his incredible speed, couldn't possibly arrive that fast! Kizaru needed a medium to travel quickly; normal movement couldn't compare to the potential speed of electrical wave transmission.
No time like the present. Doflamingo immediately had some subordinates take a Den Den Mushi and travel to the far side of the island, a significant distance away from his current position.
Using his Observation Haki, Doflamingo sensed when his men reached their destination and began the experiment.
"Young Master, we have received the signal," the Den Den Mushi on the other end responded as the call connected.
Doflamingo seized the opportunity, focusing his senses on the electrical waves forming between the two snails.
Ibes and Robin watched Doflamingo intently, holding their breath. They were astonished by his idea. It was natural, of course; they didn't understand the principles of electromagnetism – how electricity and magnetism are intertwined. The biological electrical waves of the Den Den Mushi were, fundamentally, just a type of electromagnetic wave. If Doflamingo could identify the specific signal frequency of that wave, simulate it, and transmit himself as that signal, he could undoubtedly achieve instantaneous long-distance travel. The only unknown was the stamina cost! Still, in a crisis, such an ability would be a lifesaver!
Doflamingo, possessing knowledge from beyond this world, naturally had a deeper understanding than most inhabitants of this reality – though he readily admitted Vegapunk was leagues ahead. Furthermore, Doflamingo could essentially say: Time to lay the cards on the table; the charade was over. Not only am I a Rumble-Rumble Fruit user, but I can also manipulate magnetic forces. Hell, I can even generate flames! After all, practically everyone in the pirate world seems to pull flames out of nowhere; why shouldn't Doflamingo's lightning have a fiery aspect?
Doflamingo silently focused, sensing the changes in the surrounding magnetic field. Since he wasn't a true Magnet-Magnet Fruit user, sensing these fluctuations wasn't effortless.
His fruit development had long shifted towards exploring electromagnetic waves. After all, the "Railgun" concept from a certain manga he knew had always intrigued him. Having obtained the Rumble-Rumble Fruit, Doflamingo certainly wouldn't pass up developing such a powerful technique, especially since someone else had already done the conceptual groundwork for him; Doflamingo could simply adapt it, saving time and effort.
Silence. Doflamingo stood perfectly still. Yet, within his mind's perception, he could sense even the heartbeats of Robin and Ibes, hear the faint, minuscule breathing of the Den Den Mushi nearby. Nothing escaped him. Slowly, step by step, he probed deeper, searching.
After a while – during which Robin and Ibes dared not make a sound, watching with rapt attention, hoping for a miracle – Doflamingo spoke.
"I've finally sensed it," he said, excitement clear in his voice.
"Really?" Robin's face lit up with a joyful smile.
"Congratulations, my Lord," Ibes offered her felicitations, addressing him with reverence.
"Fuffuffuffuffu," Doflamingo chuckled, clearly pleased. "Now then, watch closely." He was about to show Robin and Ibes something truly astounding.
"Human Data Transmission!" Doflamingo announced, his voice firm and resonant.
As Robin and Ibes heard his cry, Doflamingo vanished before their very eyes.
A moment later, Doflamingo's voice echoed from the Den Den Mushi connected to the far side of the island. Robin quickly responded.
"Onii-chan, did it work?" Robin asked eagerly.
"Fuffuffuffuffu! Not bad at all. It was a success!" Doflamingo replied with a laugh.
"Human Data Transmission!"
Just as quickly, Doflamingo reappeared beside them. The two girls rushed towards him excitedly, celebrating his success.
Doflamingo, equally pleased, affectionately patted Robin's head and gave Ibes's hand a light squeeze.