In this world, it's the most direct and intuitive way to quantify a fighter's physical combat strength—excluding Haki and Devil Fruit abilities.
For reference: a regular adult male, after undergoing basic naval training, would have a Douriki of just 10.
Take Spandam, for example—the infamously weak CP9 commander from Enies Lobby. His Douriki score? A pitiful 9.
In the Navy, Douriki is used as a benchmark to measure the strength of low- and mid-ranking personnel.
At Zephyr's Naval Academy, it's also an important part of student evaluation.
To enroll, the minimum requirement is 80 Douriki.
To graduate, the baseline is 500—with no upper limit.
Of course, Douriki is only one of many graduation criteria. Combat strength is important, but the Navy also assesses other qualities when deciding who qualifies for graduation.
Not long after, Zephyr led Yoriichi Tsugikuni to a wide training ground. Before them stood a massive stone wall, five meters tall and equally wide and thick. Embedded into the side was a small screen—currently displaying a single number: "0".
Zephyr walked up and tapped the stone gently with his knuckles, then turned to Yoriichi and said,
"Yoriichi, this is the machine we use to test Douriki."
"This entire stone wall is made of pure seastone—extremely durable. When you strike it, the force gets measured and converted into a Douriki value, which shows up on that screen over there."
As he spoke, Zephyr extended two fingers and gave the wall a casual knock—light, almost lazy in its motion. But the moment his fingers made contact, a deep rumble echoed out. The giant seastone block visibly shifted back several centimeters.
The screen flared to life, the numbers blinking and jumping rapidly before finally stabilizing at: 1213.
Zephyr seemed quite pleased with his demonstration. He smiled faintly.
Ten seconds later, the wall began sliding slowly back to its original position, like a spring recoiling into place.
Yoriichi was entranced. It was his first time seeing a device that could measure raw power so directly.
Still, he couldn't help but feel a little skeptical.
That wall was huge. Could a normal person even budge it?
Zephyr had only pushed it back a few centimeters and still scored over 1200. Would a regular person even register a number on that screen?
"Come on, Yoriichi. Give it a try. Use your strongest strike!"
Zephyr pointed at the wall, grinning.
Yoriichi, brimming with curiosity, stepped forward. He planted his feet firmly in a basic horse stance and, without ceremony, threw a heavy punch directly at the wall.
The force exploded out and slammed into the stone.
But the wall didn't move an inch.
However, the screen beside Zephyr flickered to life again, the numbers climbing before halting at: 520.
"Heh, that all you've got?"
Zephyr glanced at the display with a mocking tone. But his eyes were smiling.
Yoriichi suddenly stepped back, hand flying to the hilt at his waist.
With a controlled breath, he drew his blade.
A crimson fire danced across the blackened edge of the sword, casting a ruddy glow on his youthful face.
Breath of the Sun – Third Form: Raging Sun!
The slash rang out like metal crashing against metal.
Unlike the dull rumble earlier, this strike rang clear and sharp. As the blade struck the seastone, the entire wall lurched, driven back by several meters before finally grinding to a stop.
Zephyr's screen lit up again—this time the numbers shot upward and landed on: 5333.
For a moment, his expression cracked—just a flicker of surprise—but almost immediately, he recomposed himself and muttered calmly:
His voice was steady, his face neutral. But inside, his thoughts were in chaos.
5333 Douriki. What did that mean?
To put it into perspective: most Vice Admirals in the Navy—excluding Devil Fruit users—barely range between 2000 and 4000.
Only the absolute top-tier Vice Admirals—setting aside Garp, of course—might reach 5000.
Luffy, during the Enies Lobby arc, likely clocked in just over 5000 while using Gear Second. At that point, he had already defeated two Warlords and was being branded as one of the "Worst Generation."
Without a doubt, anyone with 5000+ Douriki couldn't be considered obscure, no matter where in the world they were.
And now, this teenage boy—picked up by Garp on a whim—had already reached that level?
Zephyr couldn't hide his shock… but he could suppress it.
"Yoriichi! You'd better train hard from here on out."
"A mere 5000 Douriki? You've got a long way to go."
"When you can do what I can, then you're barely ready to set sail."
With that, Zephyr stepped up to the wall again.
He took a deep breath. Then, he unleashed.
The seastone wall went flying, shoved back dozens of meters. The display beside him shot up to 7000, then glitched—flickering into unreadable gibberish: 00000.
A mechanical whimper rang out as the wall hit the end of its track. Something underneath snapped. The base shattered, and the massive slab went rolling even farther across the ground.
"It takes at least 1000 Douriki to even move this wall. I'm probably sitting around 10,000," Zephyr said with faux modesty.
"You've got a long road ahead of you, kid. Stick with me—I'll turn you into a fine Marine."
He turned to Yoriichi, whose jaw was hanging open, and smiled.
"Come on. Let's check out the rest. Starting tomorrow, your training begins—with me."
Without a glance back at the smoldering test apparatus—now cracked and wheezing—Zephyr led the boy away.
Shortly after, a group of instructors from the Academy arrived. Staring at the wreckage of the testing grounds, they stood in stunned silence.
Yoriichi spent the entire day glued to Zephyr's side, touring the Naval Academy. In the afternoon, they even walked through Marineford itself.
Everywhere they went, they bumped into familiar faces—old comrades, former students, admirers in uniform. Zephyr was in a great mood, laughing, exchanging greetings, and proudly introducing Yoriichi to everyone they passed.
"Oh! XXXX, you're back?"
"This kid? Just took him in."
"His power? Eh, nothing special. Scored just over 5000 Douriki on his first day. Still green."
Yoriichi lost count of how many people Zephyr gave that same speech to.
But between the introductions and the stroll through Marineford, he was starting to get a feel for the place—and for Zephyr's immense network.
By nightfall, exhausted from the long day, Yoriichi returned home.
He sat beneath the eaves of the porch, leaning against a pillar, gazing up into the sky.
"The night sky in this world… it's even deeper than the last one."
"And the stars… they shine so much brighter."