The Calm Belt.
Aboard Garp's dog-headed warship, two figures blurred across the deck, their clashes triggering occasional shockwaves that rippled through the air.
One of them was Sean; the other was Bogard.
As Garp's adjutant, Bogard was naturally formidable. Though he hadn't eaten a Devil Fruit, his mastery of the Marine's Rokushiki and his swordsmanship were both exquisite.
Yet, at this moment, Bogard was slightly surprised.
It wasn't that Sean was overwhelmingly powerful—after a few exchanges, Bogard had already gauged the boy's strength. He was roughly at the level of a Marine Headquarters Captain—specifically, one of the more capable elite Captains.
To reach this level at fifteen was certainly impressive, but in Bogard's eyes, it wasn't unheard of. If he exerted thirty or forty percent of his true strength, he could easily defeat Sean.
What truly surprised Bogard were two things.
First, Sean's swordsmanship was crude. It was almost purely the application of basic strikes, completely devoid of any refined techniques or named forms.
Second, despite the simplicity of his moves, the power behind every single strike was staggering.
Bogard was certain this wasn't due to raw physical strength, nor was it the result of Armament Haki coating. Most crucially, throughout the fight, Sean emitted a certain pressure. Even Bogard felt its effects, finding his own strength suppressed by roughly ten percent.
It wasn't a mental pressure, nor was it a physical one. It was a peculiar sensation Bogard had never experienced—an oppression that seemed to act directly upon the soul, causing a primal tremor that made the very air feel heavy.
In truth, this was Reiatsu—spiritual pressure. At its core, it was the act of imposing one's soul upon another. Bogard's analysis was spot on.
"Sean, is your swordsmanship self-taught?" Bogard asked as they separated once more.
"Yeah. I spent three years alone on a deserted island, just messing around with branches," Sean replied.
"That explains it..." Bogard nodded, instantly filling in the blanks.
It made sense that Sean had lacked systematic instruction. Given the unique nature of his power, if he ever received formal training in swordsmanship, his future achievements would undoubtedly be legendary.
If Sean knew what Bogard was thinking, he would have likely gone on a frantic rant.
What could he do? This was simply how a Shinigami fought. No matter how you sliced, the essence was always just... slicing!
After all, combat for a Shinigami was fundamentally a battle of Reiatsu. Most of their skill lay in combining that spiritual pressure with their swordplay—similar to how some in the One Piece world combined Conqueror's Haki with their blades.
While every Shinigami learned the four basic arts—Zanjutsu, Hakuda, Hohō, and Kidō—with the exception of someone like Kenpachi Zaraki, the most important factors remained the Zanpakutō and Reiatsu. Only with sufficiently powerful Reiatsu could the four basic arts be truly elevated.
Consequently, Shinigami didn't obsess over flashy moves; they focused on the direct application of basic strikes. Even with various schools of thought, the differences were merely in how those basics were applied. Among the major figures Sean knew, he had never seen anyone use complex or ornate sword techniques.
Aside from cutting, it was just more cutting. Simple and brutal.
In contrast, once a swordsman in the One Piece world reached the level of a Master, they were less like swordsmen and more like mages. They could effortlessly launch wind blades or, like Zoro, conjure an entire tornado.
Essentially, they were wind mages.
The two systems of swordsmanship were entirely different. However, they weren't mutually exclusive. After all, the swordsmanship of the Shinigami world lacked true long-range attacks—unless one was using the abilities of a Zanpakutō.
'If I use spiritual power to augment a Master's flying slash, what would the result be?' Sean wondered. This was one of the directions he intended to explore in the future.
'''
The journey from the East Blue to Marine Headquarters took roughly twenty days. Sailing ships were simply too slow; Garp's massive warship had a top speed of about ten knots, with a standard cruising speed of only seven or eight.
During the return trip, Sean spent his time either practicing swordsmanship with Bogard or being beaten by Garp.
Actually, Sean was starting to regret asking Garp to guide his physical training. The old man's hand-to-hand combat was undeniably powerful, but his teaching method was... unconventional.
Sean had lost count of how many times he had been punched clean into the ocean. It was a good thing he wasn't a Devil Fruit user.
Still, the gains were substantial. Having a mentor and a sparring partner provided progress that far exceeded his solitary training on the deserted island.
'System, multiply today's swordsmanship gains as quality points.'
[Item to Multiply confirmed. Determining random multiplier...]
[Ding! Today's swordsmanship training gain is 2. Multiplier is 5x. Multiplication complete.]
'Open status panel.'
[Sean Campbell]
[Zanjutsu: Lv.3 (0/1000)]
[Hakuda: Lv.3 (350/1000)]
[Hohō: Lv.3 (400/1000)]
[Kidō: Lv.2 (20/300)]
[Reiryoku: 1780]
[Zanpakutō: None]
With the addition of those ten experience points, his swordsmanship had just leveled up. Suddenly, a deeper understanding of the way of the sword flooded into Sean's mind.
Ten points of experience a day might seem small, but back on the island, a full day of training usually yielded only 0.1 experience—sometimes even less. Without the occasional high random multiplier, growth had been agonizingly slow.
But that was normal. The Shinigami system was never meant for rapid growth—unless you had protagonist armor, of course.
Interestingly, even though he was learning the swordsmanship and physical arts of the One Piece world, the status panel still categorized them under Zanjutsu, Hakuda, Hohō, and Kidō.
Sean realized that these categories weren't strictly limited to the Shinigami system; other styles could be integrated into them. In other words, this was a fusion of two different worlds, creating a version of the four arts unique to Sean.
He didn't need to follow the Shinigami path exclusively.
After sword practice ended, Garp strolled over with his usual brashness, announcing that he had something new to teach Sean.
"Listen up, kid! Watch closely—this is Soru, one of the Marine's Six Powers!"
Garp vanished in an instant, reappearing over ten meters away the next second.
Watching this, Sean couldn't help but marvel. Garp truly deserved his reputation as the strongest physical combatant in the Marine. Even with his spiritual power enhancing his senses, Sean still couldn't keep pace with Garp's speed.
"Well, kid? Got it?"
"Uh... Vice Admiral Garp, aren't you going to explain the principle behind it?"
"Principle? What the hell is that?"
'Right... I should have expected as much.'
Having read 'One Piece', Sean already knew how Soru worked regardless of whether Garp explained it. Still, was this really a proper way to teach?
"Bwahahaha! You've got no talent for physical combat, kid!"
Seeing the look of sheer exasperation on Sean's face, Garp burst into a shameless fit of laughter. In that moment, if he actually stood a chance against Garp, Sean would have charged forward and slapped the man silly.
'No wonder Luffy was still so weak when he first set sail...'
"Sean, I'll explain the principles and training methods for Soru in a moment," Bogard interjected, unable to watch Garp's "teaching" any longer.
"No need. I think I've already got it!"
As he spoke, Sean vanished. A second later—'BOOM!'
A human-shaped hole smashed right through the ship's bulkhead.
Garp and Bogard stared, eyes wide with shock. He learned it just like that? No... something was off.
It looked like Soru, but it felt different. Garp, in particular, had seen the movement clearly. When Sean activated the technique, he had only kicked the ground nine times!
Normally, one needed to kick the ground at least twenty times to generate enough explosive thrust for such high-speed movement. Nine times? That was impossible—completely illogical!
Meanwhile, inside the cabin, Sean climbed out from a pile of splintered wreckage.
"Just as I thought. By fueling Soru with spiritual power, I can generate sufficient thrust with fewer than ten kicks."
"However, this burst of power is a bit difficult to control. I'll need to refine it further. I have to manage the spiritual power with more precision. If I can do that, I might be able to reduce the number of kicks to around five without losing any speed."
Resting his chin in his hand, Sean sank into deep thought. If any Marine officer proficient in Soru had heard this, they would have questioned the very nature of their existence.
'We train ourselves to death just to squeeze in one or two more kicks for a tiny bit more speed, and this guy is trying to figure out how to do fewer? Give us a break!'
Sean: "Sorry, but I'm a Shinigami!"