No matter the era, Emiya Shirou knew that Black Zetsu's trust was the absolute top priority. As the grand puppet master of the entire ninja world, its trust was directly tied to the success or failure of Shirou's own millennia-spanning scheme.
Therefore, every decision, no matter how trivial, was run by Black Zetsu. Shirou would use any means necessary to continuously reinforce the illusion that they were a team, that Black Zetsu's input was vital.
Most of the time, he'd even manipulate it into helping him achieve his own goals. Even something as seemingly minor as exposing Obito Uchiha's identity was presented as a joint decision, despite it being completely irrelevant to their grand plan.
"Hmph, that idiot," Black Zetsu's smile grew more sinister, its disgust for Obito having long since peaked. "He's just a pawn Madara left behind to keep us from kicking him out of the plan, yet he actually thinks he has his status."
"In a world so polluted by lies," Shirou sighed, as if struck by a profound revelation, "recognizing one's true identity and holding onto one's original heart is always a difficult thing. Black Zetsu, perhaps we too have grown accustomed to this era of deception. It is only our belief in Lady Kaguya's power to bring eternal peace that has sustained us."
"Don't worry about such things," Black Zetsu quickly interjected, sensing a hint of existential dread in Shirou's tone. "Wei Yuan, when Kaguya is revived, everything will return to its origin."
"Perhaps," Shirou said, casually changing the subject, his voice laced with just enough doubt to be believable. "By the way, if we just waltz into Konoha, will it cause trouble? I seem to have forgotten to gather any intel from them."
He let his voice drop, feigning strategic concern. "We must first find the carrier of Orochimaru's resurrection seal. Whether we dispose of him or use him, we can't risk him leaking Akatsuki's secrets."
Black Zetsu felt a familiar wave of helplessness, followed by a fresh surge of annoyance at the Sage of Six Paths. It knew it had to restore Shirou's confidence itself.
"Obito and Itachi have just massacred the Uchiha clan," it reasoned, following Shirou's lead. "Konoha's security will be tighter than ever. It might not be a problem for me and White Zetsu to sneak in, but..."
"You, Shirou, are another matter. You're the one who needs to find Orochimaru's seal carrier. Only you have the eye for it."
"No matter," Shirou said, unconcerned. He had already prepared for his own exposure, but he continued to guide Black Zetsu down the path he'd laid. "Even if I'm discovered, it doesn't matter. Orochimaru mentioned there are many people in this village who know me. Perhaps it can be resolved peacefully. I have already mastered the art of ninja deception. I will deceive them."
Black Zetsu did not believe him.
Not for a second.
To be honest, Shirou was reliable in every conceivable way. You could throw a half-baked plan at him, and he'd execute it flawlessly. The only thing he was unreliable about was his own self-professed ability to lie.
How on earth did he have such confidence?
Back when he'd asked Shirou to deceive Madara, the man had prefaced his lie by announcing, "I'm not very good at lying," which nearly torpedoed the entire operation. It was only Madara's all-consuming hatred for Tobirama that saved them.
But Black Zetsu had been terrified, constantly worried that Shirou's complete inability to lie would ruin everything.
So, while Shirou often claimed to have mastered the ninja art of deception, Black Zetsu had zero confidence in his lying skills. He had learned to conceal things, sure, but his method was to just go completely silent when asked a key question.
What kind of damn concealment method was that?
It was more like a confession!
"Are you sure you can hide it from those Konoha people?" Black Zetsu asked cautiously.
"Trust me, Black Zetsu," Shirou nodded, radiating a confidence that only made Black Zetsu more anxious. "I have already mastered the ninja's means of deception. If my identity is discovered, I will tell them I came to pay respects to the First Hokage."
"Coincidentally, I didn't see him in the underworld. After being revived by Orochimaru, I broke free and came to Konoha to visit his grave."
"Sounds... plausible," Black Zetsu mumbled, a nagging feeling that something was off. Shirou didn't seem to be lying; it sounded a bit too much like the truth. "And if someone asks about your relationship with the Akatsuki?"
"No relationship," Shirou replied with a blank face, then frowned. "Actually, I don't think it's necessary to lie about that. The Akatsuki carries out the will to bring eternal peace to the world. It was I who told Madara this method. We believed he was a fellow traveler on the path to peace. This will was passed down and created the current Akatsuki."
This statement was, infuriatingly, flawless. It could convince anyone. The key problem was, Shirou seemed to be telling the truth.
"This... sounds like the truth, right?" White Zetsu whispered, equally confused.
"Wei Yuan," Black Zetsu sighed, a headache already forming. "Your lies and concealment are still as clumsy as ever."
It was a vexing situation. Shirou's honesty and kindness were precisely what had earned Black Zetsu's trust, but they were also what made it so uneasy.
His honesty meant he was unlikely to lie to others, and his kindness could be easily exploited. Fortunately, this little vexation was, for now, more beneficial to it than not.
"You don't believe me?" Shirou seemed to frown with a hint of dissatisfaction. "I used the Flying Thunder God Technique to deceive Obito in battle."
"I will always believe you," Black Zetsu sighed, its trust in Shirou infinite. "In the ancient era, you were a true genius." It kept its final evaluation to itself: Except for lying, he's practically omnipotent in everything else.
"Alright. Even if an accident happens, it doesn't matter," a faint light flashed in Shirou's eyes, his Rinnegan looking so reliable. "I have learned a lot from Senju Tobirama. I will no longer reject the uses of great power, as I did in the past."
-----
Konoha was on high alert.
The Uchiha massacre had put everyone on edge. ANBU patrolled constantly, and the village's protective barrier was always active. They had even suspended all external missions. But for Shirou, these defenses were meaningless. He had mastered the Flying Thunder God Technique.
"Let's go pay respects to Hashirama first," he said, choosing the Memorial Stone on the back mountain as their first stop.
"So," White Zetsu's mouth twitched, remembering Shirou's "lie" about paying respects. "Is it really the Lord Emiya… such an expert at deception?"
"Hmph," Black Zetsu grunted, looking at Shirou's back. "After all, Hashirama once carried his hope for peace in this world. A meaningless peace."