While Uchiha Itachi was still running countless calculations through his mind, Kaigaku and Agatsuma Zenitsu had already begun fighting in the footage.
"You've devoured so many people you can't even tell right from wrong anymore?" Zenitsu shouted.
Facing his furious junior, Kaigaku only bared his teeth in a grin. "Oh, I can tell just fine. What's wrong? Still haven't inherited that old man's techniques? Show me what you've got—your best move. Come on."
"Go ahead. Don't hesitate. Try attacking me."
Their clash was unbelievably fast—so fast it might as well have been lightning itself.
Compared to Zenitsu, Kaigaku, who had mastered more forms, clearly held the upper hand.
"Is it because it's too straightforward?"
Uchiha Sasuke watched as Zenitsu was pushed back, and the strengths and weaknesses of Thunder Breathing, First Form—Thunderclap and Flash—became clearer than ever.
It was an attack that abandoned all defense in favor of pure offense. Against opponents slower than oneself, it worked perfectly. But against someone equally fast, relying solely on the First Form exposed a fatal flaw.
It was far too direct.
Almost the moment Sasuke reached that conclusion, Kaigaku, all the while taunting him with insults, slammed Zenitsu down to the ground.
Zenitsu seemed to realize something as well, as if making a decision deep within, yet he was still blasted away again.
As a demon, Kaigaku's advantage was overwhelming.
"Lightning crashes and thunder roars—my strikes will tear your body apart again and again. My power will scorch your brain. After becoming a demon, I've perfectly mastered Thunder Breathing!"
"Ha! I'm special. Not like you. Not like any of you. That old man was wrong in the end."
Hearing those words, the falling Zenitsu finally snapped. In midair, he twisted his body, halting his descent. He planted himself against the wall and unleashed Thunder Breathing. Countless arcs of lightning surged upward like writhing serpents, terrifying in their intensity.
The wall beneath his feet shattered under the force.
Everyone watching the diary couldn't help but hold their breath. So even without chakra, such explosive power was possible?
"Sorry… senpai."
Amid the dance of lightning, Zenitsu leapt upward, his form transforming into a streak like a lightning dragon as he slashed toward Kaigaku.
"Thunder Breathing, Seventh Form—Flaming Thunder God."
Zenitsu's voice was calm.
With that single strike, Kaigaku's head was severed.
Blood sprayed outward as his body slid downward.
"I… I didn't expect that… what kind of Breathing technique was that?"
Shock filled Kaigaku's severed head.
"That speed… I've never heard of anything like it."
"What did you use? Damn it—I knew that old man favored you! He only taught you that move, didn't he?!"
Even as his head roared, Zenitsu finally mustered the last of his strength and shouted back, "That's not true! Grandpa wasn't like that! I created it myself… I once hoped that one day, we could use it together."
"Seventh Form? Thunder Breathing only has six forms. You created a seventh? You? The one who could only use the First Form? The one who cried all day? Impossible! I refuse to believe I lost to someone like you—this is insane!"
"No… I haven't lost yet. He'll die from the fall. He's out of strength. That trash will drag me down with him. Hahaha!"
As Kaigaku raved in disbelief, even taking pleasure in the thought that Zenitsu would perish with him, a voice filled with disdain cut through the air.
"Those who choose not to help others shouldn't expect anything in return."
Yushiro appeared.
"People who only seek their own gain end up with nothing. They can't accomplish anything on their own. Dying alone like that… it's pitiful."
After saying that, Yushiro caught Zenitsu midair and carried him away.
The video ended.
Everyone reflected on what they had just witnessed, realizing that there existed a kind of creature in this world called demons—beings that feared sunlight, devoured humans, and did so in horrifying numbers.
They were once human. They didn't use chakra, yet they possessed their own unique system of Blood Demon Arts.
The most troubling part was their habit of eating people. That alone would be enough to plunge society into panic.
The shinobi world had never truly known peace. Even with the major nations maintaining a fragile balance, missing-nin roamed freely, massacring entire villages or towns without consequence.
But that was still ordinary killing.
Compared to that, creatures that ate humans were far more terrifying.
"Demons possess incredible regenerative abilities. The stronger ones have 'Upper Rank' and numbers in their eyes. There may also be Lower Ranks."
Hatake Kakashi glanced at the notes scribbled across the page.
"The Demon Slayer Corps… an organization dedicated to hunting demons. Their system revolves around Breathing techniques, but they don't use chakra."
Everyone felt it was necessary to take these newly revealed demons seriously.
"So they die when their heads are cut off? It seems that surviving decapitation—or even having their bodies blown apart—is a trait unique to the Demon King."
Uchiha Itachi continued writing.
"Based on the diary, demons are divided into ranks: the Demon King, the Upper Ranks from one to six, the presumed Lower Ranks also from one to six, and then ordinary demons—the kind that can be killed in a single strike."
"Their regenerative abilities vary. Most demons likely share the same weakness: the head. Once it's severed, they should die."
After reaching this conclusion, Itachi felt somewhat reassured. Their regeneration was formidable, but they weren't invulnerable. If they could be cut down, then they could be killed.
And if that was the case, even Mangekyō Sharingan users wouldn't be at much of a disadvantage. The concern he had earlier—about Sasuke suffering a major loss in the Infinity Castle—eased slightly.
"That Kaigaku… what a piece of trash."
Uchiha Sasuke clicked his tongue as he watched Zenitsu's pain in the diary, a trace of understanding rising within him.
He knew that feeling all too well.
He, too, had once had a brother he admired, only for that brother to betray their clan and lead it to destruction. He had placed endless expectations on him—only to have them shattered.
Zenitsu's revenge against Kaigaku was no different from his own desire for vengeance against Uchiha Itachi.
At their core, they were the same.
And because of that, the scene struck him deeply.
This was how it should be—those who betrayed their own must pay.
He understood it completely.
Zenitsu had already avenged his grandfather.
But when would he avenge his own family?
Three years.
He had seen it in Kaede Kitahara's diary. He would need three more years of tempering before he could gain the strength for revenge.
In three years, he would become stronger.
Stronger than he had ever been.
That night, everyone was shaken by the existence of these creatures called demons, especially the fact that they were once human and seemed to be something that could be controlled—meaning a full-scale demon disaster was not impossible.
The thought left many restless, unable to sleep.
Only Kaede Kitahara, completely unaware, slept soundly.
Early the next morning, Asama Sandayu, the manager of Kazahana Koyuki, personally came to visit.
Kaede Kitahara looked at the bespectacled man standing before him, searching through his memories until he finally recalled his identity.
Asama Sandayu was not only Kazahana Koyuki's manager, but also a former retainer of her father.
After Koyuki had been taken away from the Land of Snow, he had remained by her side in disguise, protecting her as her manager.
This time, it was he who had orchestrated her return to the Land of Snow behind the scenes.
Because he was also the leader of the resistance in the Land of Snow, waiting for the rightful heir—the former daimyo's daughter—to return and lead them in overthrowing Kazahana Doto's tyranny.
Unfortunately, Koyuki had been traumatized and had no intention of returning to the country ruled by her uncle.
In the end, Sandayu had resorted to a plan—having Hatake Kakashi use genjutsu to knock her unconscious and bring her back.
Anyone capable of arranging something like that was undoubtedly a seasoned schemer.
At this moment, Sandayu was also sizing up Kaede Kitahara.
Originally, this mission had been intended for Kakashi. They had some level of personal connection, after all.
Back when Kakashi had helped escort Koyuki out of the castle, Sandayu had secretly aided him.
He trusted Kakashi's strength. The man was renowned throughout the shinobi world as the Copy Ninja. With Kakashi leading the mission, Sandayu had been confident they could reclaim their country.
But now the mission had been handed over to Kaede Kitahara.
He looked far too young.
Could he really pull it off?
This wasn't just a simple escort mission—it determined the fate of an entire nation.
Kaede noticed the doubt in Sandayu's eyes, but didn't take it to heart. Anyone in his position would feel the same.
After a brief exchange of pleasantries, Sandayu finally spoke.
"I wonder if Hatake Kakashi-senpai told you about the true nature of this mission?"
"I have a general idea," Kaede replied. "Fujikaze Yukie is actually Kazahana Koyuki, the daughter of the former daimyo of the Land of Snow. You want her to return and take the throne, right?"
He didn't bother dancing around the issue—he laid it out directly.
Seeing that Kaede understood the unspoken agreement between himself and Kakashi, Sandayu finally relaxed.
"But right now… Yukie—ah, I mean, Her Highness the Princess—doesn't want to return to the Land of Snow. She's been avoiding us."
"That's fine. Leave it to me."
Kaede Kitahara smiled faintly and nodded.