That evening, after the Uchiha's rare victory over the Hokage Faction in decades, several clan members dragged Uchiha Chen along to celebrate over dinner.
Afterward, someone suggested they head to an izakaya for a few drinks and talk about life with the young ladies.
"Then we're off, Chen!"
Uchiha Inabi hummed a jaunty tune and raised an eyebrow smugly as he teased him:
"Even if you're a great hero of the Uchiha, people should still act their age!"
"Hahaha!" The group roared with laughter, then slung their arms around one another's shoulders and headed for the red-light district.
"Damn it!"
On his way back to the clan compound alone, Uchiha Chen kicked a pebble along the road, despairing at this twisted Shinobi World:
An era when a ninja could kill without batting an eye at seven or eight years old.
An era when people could marry at fourteen.
And yet the Land of Fire's laws actually forbade anyone under eighteen from drinking, and prohibited selling alcohol to minors?
"Chen!"
Just as Uchiha Chen was about to reach the clan compound, a hoarse, magnetic voice suddenly rang out.
Uchiha Chen looked around and spotted a young man in a black kimono hidden in the shadows of a streetlamp not far away.
He wore his long hair loose over his shoulders, with black eyeliner and purple eyeshadow. Combined with his golden, slit-pupil eyes, it gave him a terrifying gaze.
When Orochimaru saw Uchiha Chen looking his way, the corners of his mouth curled up slightly, and he licked his lips.
"Lord Orochimaru!"
Uchiha Chen naturally walked over to Orochimaru's side. "You wanted to see me?"
"I got what you asked for." Orochimaru chuckled, clearly in a very good mood.
"And I've made a rather interesting discovery about the genetic material you mentioned earlier! You know where to find me."
With a bang, the Shadow Clone he'd used to deliver the message vanished.
Faced with Orochimaru's summons, Uchiha Chen fell into thought.
The Shinobi World's technological development was wildly uneven. Some things looked like futuristic science fiction from the twenty-second century, thanks to Chakra, while others were as backward as the seventeenth or eighteenth century.
Until recently, the Shinobi World's understanding of biology had barely progressed beyond the cellular level.
During the Third Great Ninja War, Uchiha Chen had let Orochimaru in on some of the biology he'd studied in high school in his previous life, hoping to learn more advanced Medical Ninjutsu and better protect his own life. In return, Orochimaru had treated him favorably on the battlefield.
If Chen hadn't been an Uchiha, Orochimaru—who appreciated him—might have taken him on as a student long ago.
But with the Hokage Faction having just suffered a setback, should he really meet with Orochimaru now?
After a long while, Uchiha Chen decided to go to Orochimaru's laboratory in the village.
After all, with the Mangekyō ability granted by his Prosthetic Eye, he reckoned he could handle Orochimaru. Besides, he was very curious about Orochimaru's "discovery."
Beneath the pitch-black night sky, a figure raced through the Forest of Death before plunging headfirst into the hollow of a giant tree.
After passing through layers of seals and traps, Uchiha Chen entered the underground laboratory.
The damp, chilly basement had many translucent glass jars lined along the walls. Inside were bizarre specimens that could make anyone lose sanity just by looking at them, and the air was filled with an indescribable stench from the mixture of chemical reagents.
Uchiha Chen was long used to this. Following the hum of the experimental equipment, he soon found Orochimaru in a laboratory, staring intently at a workbench.
"You're here? Just a moment!"
Orochimaru fiddled with a microscope and other equipment. After the instruments finished counting down, the printer behind him began spitting out sheets covered in diagrams and text.
"Take a look at these cell images first!"
With Orochimaru's permission, Uchiha Chen picked up the papers and sat down nearby.
Oval shape, indistinct nucleolus—human tissue cell. Pale cytoplasm with many small granules—neutrophil.
Uchiha Chen skimmed through the pages until he came across a cell with a cell wall and vacuole, and suddenly stopped.
A cell wall. A vacuole.
Going by his limited high school biology knowledge, cells with those features should generally be plant cells.
But,
Orochimaru had labeled this cell image:
Human Meridian Cell!
That was right. Although people in the Shinobi World looked similar to the humans of Uchiha Chen's previous life on Earth, their inner makeup was fundamentally different.
For example, people in the Shinobi World had 1.3 quadrillion cells, while people on Earth had only 40 to 60 trillion.
And people in the Shinobi World had a "Chakra Meridian System" that ran throughout their bodies, much like the circulatory system.
The cells that made up the Chakra meridians were plant-like?
Uchiha Chen thought of the God Tree planted by the Otsutsuki.
"As expected of you, Chen! You spotted the key point at a glance!"
Orochimaru turned on the sink at the workbench and scrubbed his hands. His neck twisted a full 180 degrees in an inhuman motion, his sharp, hawk-like eyes fixed on Uchiha Chen.
"I'm certain the secret of Chakra lies in these meridian cells. But for now, I'd like you to look at something else."
Orochimaru moved aside to clear a space at the workbench, gesturing for Uchiha Chen to look through the microscope he'd adjusted.
In the microscope was a long "tadpole"—a male reproductive cell.
"Chen! This cell was provided by an unnamed Special Jōnin of the Sarutobi Clan. Pay close attention to the midpiece of its tail, where the annulus is!"
Uchiha Chen activated his Sharingan and used its powerful vision to examine the "tadpole's" tail.
"There are a few semi-autonomous organelles here, similar to mitochondria and chloroplasts!" Orochimaru's voice brimmed with excitement.
"A few months ago, his reproductive cells had no such structures!
"Only two months ago, after he completed Fire Style nature transformation, did some of his reproductive cells begin carrying these organelles.
"So, following your naming convention for mitochondria and chloroplasts, I've named these organelles 'Attribute Bodies.'
"They can pass on Chakra natures!
"Families like the Uchiha and Sarutobi, who excel at Fire Style, have descendants who are almost all talented in Fire Style. That's because many ninjas in those clans have completed Fire Style nature transformation and passed these Attribute Bodies on to their descendants!"
Uchiha Chen nodded.
Nature transformation was already a highly advanced ninjutsu technique. Those capable of training in it were generally Special Jōnin or higher.
That fit the Shinobi World's tendency for a strong ninja's descendants to be skilled in the same nature transformation as their parent.
But this only verified the inheritance of Chakra natures. It wasn't exactly a groundbreaking discovery, was it?
As if he'd sensed Uchiha Chen's doubt, Orochimaru quickly produced a diagram of the reproductive cell and pointed to the spot where they'd just observed the "Attribute Body."
"Chen, do you know how many ninjutsu-type Kekkei Genkai there are in the Shinobi World?"
Uchiha Chen quickly thought through the familiar ones: Magnet, Lava, Ice, Boil, Scorch, Storm, Explosion. Then there were the less common ones: Crystal, Steel, Transparent, Typhoon, Blaze, and Swift.
"About a dozen?"
"Twenty!"
Orochimaru's voice was firm, brimming with confidence in his research.
"There are exactly twenty ninjutsu-type Kekkei Genkai! And next—"
Orochimaru's grin grew increasingly manic, but his eyes became ever clearer and more resolute, like a pilgrim who had finally caught sight of his destination.
"I'm going to show you the truth of Kekkei Genkai!"
Before you continue