After bidding farewell to the merchant ship, Leo returned to the village.
Baltimore Island truly deserved its title as a "Land of the Future," a cradle for geniuses. Yet, beneath its surface, the island was far more complex than it seemed. If Leo's birthplace, Sphinx Island, could be described as a primitive society, Baltimore had already advanced to a mechanical and steam-powered era.
Once settled in the village, Leo visited Vegapunk's home again and asked the young guards if he could study there for a while. They led him to a larger steel building, the headquarters of Baltimore's scientific community.
This island in the New World had no traditional government; it was managed primarily by a group of scientists. The islanders respected these geniuses and willingly supported their endeavors, while the scientists used their inventions to improve the lives of the residents. The island fostered a strong academic atmosphere.
Baltimore's scientists were generous with their knowledge, allowing residents to learn any technology that interested them. Such an environment nurtured the creation of geniuses. When Leo expressed his desire to study the techniques left behind by Vegapunk, the scientists readily agreed.
Vegapunk was undoubtedly the most brilliant scientist on the island. To reduce physical labor for the residents, he developed semi-mechanical animals. To improve living conditions, he designed a large-scale heating system. Later, due to funding shortages, he revised his approach and developed a steam-boiler-like heating system.
Even though Vegapunk had only changed the method of heating, his reputation as a scientist 500 years ahead of his time was well-earned. After all, before time travel existed, it had taken the world centuries to transition from fire-based heating to water heating systems.
Vegapunk's semi-mechanical animals were even more astonishing. Leo carefully studied the mechanical watchdog. Its electronic eye functioned as an auxiliary recognition system: if a stranger made a dangerous move, the dog would attack. This alone impressed Leo immensely—he couldn't imagine how such a device could be made without a central processor.
Moreover, the dog was equipped with an auxiliary weapon system. A missile launcher was mounted on its back, with magazines that opened automatically during attacks. Although it could carry only two missiles, their destructive power rivaled that of conventional cannons. Unlike bulky old-fashioned artillery, this system was portable and fully automatic, making it versatile. For instance, if the recognition system and weapon were installed on a seabird, it could function as a biological drone. A warship equipped with such technology could essentially become an aircraft carrier.
In short, with the electronic eye and small missile system, Vegapunk truly understood the "romance of invention." Leo believed he could become a kindred spirit to Vegapunk.
While observing the mechanical dog, Leo had an idea and said to the guard, "Sir, what if the explosives in the missiles were replaced with liquid? Wouldn't that be more effective?"
"Why do you say that?" The guard clearly didn't understand Leo's reasoning.
"Baltimore is extremely cold; water can freeze instantly. If the target is wet after the weapon explodes, it will freeze quickly. The lethality of this approach far exceeds ordinary explosives."
The guard paused, impressed by Leo's ingenuity. "Wow, little one, how did you come up with that? Are you a genius too?" Islanders on Baltimore clearly admired clever minds.
"Uh… this wasn't my idea. It was Cao Cao's."
"Cao Cao? Just the name alone suggests someone extraordinary. Baltimore welcomes bright minds with creative ideas. I'd love to meet him."
"Um… Uncle Garp, do you have a wife?"
"What?"
"Haha, never mind." Leo clearly didn't want to reveal Cao Cao's true identity—a prime minister fond of married women—so as not to leave a bad impression.
After a brief conversation, Leo immersed himself in study. Seeing his focus, the guards quietly left the room, leaving him alone.
When you are fully absorbed in something, time flies. Unnoticed, a month passed. Leo had almost completed his research on semi-mechanical transformation technology and planned to use it to develop his own weapons.
Among the blueprints, he discovered a concept for a laser weapon. Vegapunk had conceived the idea in his youth, long before encountering Admiral Kizaru. Leo marveled: even as a child obsessed with toys, Vegapunk was already thinking about developing his own advanced technology.
Though Vegapunk's laser weapon remained theoretical, Leo could bring it to fruition using his memories from a previous life.
He also remembered Franky, the seemingly rough but brilliant inventor who had created a cola-powered device. Leo decided to use his Devil Fruit abilities to supply the energy needed to power the laser weapon.
With the idea in mind, Leo immediately began work. Vegapunk's lab was filled with scrap metal, and all the equipment for transformations was ready. The lab rang with the sounds of hammering, sparks flying from welding.
After several days, Leo completed a small generator. Using his Devil Fruit power, he made the water in the generator spin rapidly, converting mechanical energy into electricity. This electricity was stored until it reached the power required to activate the laser weapon.
Next came the laser emitter. Vegapunk had already completed the theoretical research and generated photons but had stalled on the next step. Leo surmised that Vegapunk later studied Kizaru's Pika Pika no Mi to enhance beam intensity. For Leo, this was simple: he used his fruit powers to continuously drive the generator, producing sufficient energy to convert into photons, then amplified the beam through reflection and absorption.
Finally, the focusing stage was easy—like using a magnifying glass to light a paper. A single lens sufficed. After several days without sleep, the first laser weapon in the One Piece world was complete.
Due to technical limitations, Leo made it ship-mounted, naming it L·Photon 1. It consisted of four parts: a water tank, hydro-generator, battery, and laser emitter. There was no start button; activation depended on Leo triggering his powers to spin the water. The console only displayed an energy bar and a fire button.
Eager to test it, Leo charged the weapon. Upon pressing the fire button, photons gathered, and after a two-second charge, he released it. A flash erupted from the barrel, cutting a tree in half. Only 2% of the energy had been used.
"Wow! It worked! And it's insanely powerful!" Overwhelmed with excitement, Leo realized he had built a laser weapon even Vegapunk hadn't.
Laser output depended on charging time: 2 seconds minimum, 7 seconds maximum. After 7 seconds, the focusing mechanism would overheat. Full-power shots consumed 32% energy, allowing only three maximum-power firings.
Testing maximum power, Leo held the button for seven seconds. The weapon emitted a cross-shaped beam that slowly contracted. When he released it, a red laser streaked into the forest, exploding into a crater two seconds later.
Tears streamed down Leo's face. "This is what I wanted… Mechanical ascension really is my ninja path."
Over the next three months, he refined the laser cannon to combat readiness, installing two aboard his ship.
While reviewing Vegapunk's notes, Leo found clues about the scientist's travels and decided to follow them.
During his months on Baltimore Island, Leo developed a close rapport with the scientists. Grateful for their generosity, he proposed improvements to the heating system, increasing efficiency and reducing costs. The visit proved mutually beneficial.
Before departing, Leo gave most of the treasure he had seized from pirates to the scientists, who gladly accepted it. With the funds, many research projects could continue.
Once at sea again, Leo sensed that if he could find Vegapunk, he might have the chance to join MADS—a group including Vegapunk, Vinsmoke Judge, Queen, and Caesar. Any one of them could be a future top scientist, and the thought of working with them thrilled him.
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All the fanfiction is 30-chapter ahead but this "One Piece: Shadows of the Throne" is 30 chapters ahead there