Sixteen years old, the Fourth Mizukage

"You really are… the type to act on whatever thought pops into your head, Rei Kaguya."

Before the phantom maintained by the Magic Lantern Body Technique, Nagato, who had originally been sitting in the palm of a giant Buddha statue and meditating in deep thought, could not help pressing his fingers against his brow. He sighed, unable to hide his exhaustion.

"It is merely changing with the times and acting according to the situation. After all, after an event great enough to completely alter the world's balance has occurred, we cannot conservatively cling to every strategy made before that upheaval happened, can we?"

Rei Kaguya's phantom tilted its head and spoke in a casual tone.

"When an opportunity reveals itself, a leader must possess enough courage and resolve to make a decision. If you are always one step slower than others, then even a once-vigorous spirit of ambition will eventually be worn away along with it…

"When you decided to transform the Akatsuki into a platform for peaceful communication among the various powers of the shinobi world, you were rather decisive, Nagato. Why is it that now, when a perfect opportunity has been delivered to your doorstep—one that can truly make all sides recognize and trust the Akatsuki's transformation—you have instead become so hesitant?"

"I would not say I am hesitant…"

Nagato sighed and gazed at the rain before him, a rain that seemed as though it would never end. Somewhat lost in thought, he said,

"I am simply rather envious of your way of thinking. No matter what happens, you instinctively search for the opportunity hidden within it and maximize its benefits… If it were me, even if I already held the method to solve the moon's descent in my hands, I doubt I would have the mind to use this information gap to secure the greatest possible advantage for the Akatsuki's development at this very moment."

"You will get used to it slowly."

Rei Kaguya's phantom sat down beside Nagato. Raindrops passed through his illusory body, stirring a blur like rippling water. Only those white eyes remained unchanged, shining with a light that seemed capable of piercing straight into the human heart.

"In the past, Nagato, you were alone. You were a child who only needed to look after your own friends to feel at ease, a supporting role who felt satisfied so long as he protected the ideal that his best friend had once brought into being. So when you encountered difficulties, it was enough for you to stand up and resolve them. That alone would allow you to accomplish your goal."

"But now, things are different."

"Now, you are the leader of the Akatsuki. You are the practitioner and executor of the ideal of achieving peace in the shinobi world through communication. You are the one who allows the power of the Rinnegan, a power that once belonged to the Sage of Six Paths, to shine again.

"As the leader of an organization, you have the responsibility to fight for every legitimate benefit your subordinates deserve. As a herald of peace, you must use legitimate means to make more people hear your ideal, understand your ideal, and join your ideal. As the wielder of the Rinnegan, you have the obligation to openly and honorably display your power and will to the world…"

"Since you already possess strength and status great enough that your every action can affect the course of history, then rising with the tide of history and guiding it through legitimate means toward the direction you desire should become your instinct."

Listening to Rei Kaguya's words, which sounded both like guidance and preaching, a faint look of realization appeared on Nagato's face. He wiped away the rainwater that had blurred his vision and said with complicated emotion,

"Is this the insight you gained after becoming Mizukage, after becoming a leader?"

"Before that."

Rei Kaguya gave him a light answer that plunged Nagato into silence once more. Only after finally calming himself again did Nagato smile bitterly.

"Before that, huh? Then Jiraiya-sensei's view that you are the reincarnation of a god born with knowledge may not be entirely baseless… Otherwise, I truly cannot imagine what sort of childhood experience could naturally give rise to such a mature way of thinking."

"After all, at that time, I was only a 'man' whose goal was to become the Fourth Mizukage."

Rei Kaguya's phantom shook his head, a myriad of emotions flashing through his eyes. Nagato, who keenly caught the key word in that sentence, narrowed his eyes. Then, with a sense of incomprehension and unwillingness to believe, he asked softly,

"And now, you are not?"

"The time is approaching. I have already resolved myself to step onto the path of becoming a 'god.'"

Rei Kaguya took a deep breath. Then he turned and stared at Nagato's suddenly constricted purple Rinnegan, asking in a seemingly casual tone,

"Among all the words I just said to you, which one do you think is the most important?"

"…Responsibility?"

While receiving Rei Kaguya's thought waves, which contained almost no emotional fluctuation, Nagato answered with his mind in turmoil.

"Responsibility? As a catalyst that matures people and pushes them forward, responsibility is certainly important, but it is not the most important thing."

Rei Kaguya shook his head, signaling that Nagato could reconsider his answer.

This time, Nagato thought for much longer.

He repeatedly savored the words Rei Kaguya had said, words that mixed persuasion with instruction. He analyzed them layer by layer, searched through his memories, and racked his mind, trying to combine them with the different impressions Rei Kaguya had left on him at various points in the past to find the answer to this sudden question.

Rei Kaguya's phantom did not urge him.

He simply raised his head in silence, gazing at the endless rain clouds above the Land of Rain, and at the massive prison even higher above those clouds, whose falling momentum was gradually being halted.

"Is it… legitimacy?"

After a long time, Nagato finally raised his head slowly and asked in a low, uneasy voice.

Hearing that answer, even though Rei was only a phantom formed from thought waves and chakra, and even though only his eyes could show a complete shape, in Nagato's eyes, Rei Kaguya still revealed a smile from the bottom of his heart, one filled with relief.

"If you can see that, then I can rest assured and officially entrust the future task of correcting me to you and your successors, Nagato."

Rei Kaguya's answer sounded as though a weight had been lifted from his shoulders.

But for Nagato, he still did not quite understand why Rei Kaguya had to do this. So he could only continue looking into Rei Kaguya's eyes, waiting for the other party to answer his doubts.

"But why? Why choose to become a 'god'? And why… say so much to me?"

"Because you are, relatively speaking… rather realistic?"

Rei Kaguya thought for a moment about reasons aside from strength, then finally reached that conclusion.

"You may not understand when I say this, but based on my own observation of you, and based on the information I have obtained through certain means about the future without my existence, among all the shinobi in the shinobi world with outstanding strength, you are the one whose way of thinking is the most realistic."

"What does that have to do with anything?"

"Mm. I have already made up my mind to solve every problem I can see now and every problem that may appear in the future while I am still alive. Such an idealistic approach taken to the extreme—is that not the act of becoming a 'god' who surpasses humanity and guides humanity? Once I become a 'god,' how can that still have anything to do with reality?"

Rei Kaguya's phantom raised his hand and, as though out of habit, reached toward Nagato's forehead.

Then, just as Nagato worked hard to suppress his instinct to dodge, Rei stopped at exactly the right distance, just short of touching his forehead. In an incomparably solemn tone, he said,

"Because I have chosen the path of idealism, I must entrust the task of supervising and correcting the mistakes I make in my choices and on my path to someone realistic enough in thought, and someone capable of truly passing down that awareness and way of thinking."

"Whether one is a 'man' or a 'god,' if one wishes to reach the core of one's ultimate goal, one cannot do without consistently upholding the word 'legitimacy.' This 'legitimacy' can be universal morality, such as public order and accepted ethics, or it can be a willful, self-centered, arbitrary logic. But no matter which form of 'legitimacy' one insists upon, it absolutely cannot waver, compromise, or retreat."

"If 'legitimacy' wavers, then the original heart walking that path will become clouded. If 'legitimacy' begins to compromise with reality, then a 'god' will fall back into a 'man' and lose the resolve to cut through thorns, split mountains, and part seas without ever turning back. If 'legitimacy' retreats before hardship, then the path I have chosen ends there."

At this point, Rei Kaguya paused briefly, waiting for Nagato to keep up with his thoughts before continuing.

"If a 'man' with ideals loses his legitimacy, then waiting for someone capable of correcting him is still relatively easy. But if a 'god' loses his legitimacy, falls into a 'man,' yet still clings stubbornly to the position of a 'god' and refuses to step down, then countless 'men' with ideals must charge forward one after another, risking and sacrificing their lives, before it may be possible to drag him completely down from the altar."

"I know many things. Enough that I, with my power, can walk smoothly on the road to ascending the position of 'god.' But I cannot guarantee that those things can answer every problem that may appear in the future, nor can I be certain that I will always uphold 'legitimacy' the way I did at the beginning. If one day in the future, I lose the 'legitimacy' I insist upon, I may perhaps create a world even more terrifying and despairing than this chaotic age of conflict."

"To prevent that from happening, I will have to ask you to become the first 'man' who raises the banner against me when I fall back into a 'man,' and to pass down that vigilance and opposition toward 'god' again and again, Nagato."

Hearing that he had been entrusted with a mission that might only be activated at some unknown point in the future, Nagato's serious face could not help showing a helpless bitter smile. He shook his head and sighed in resignation.

"Just because I have the Rinnegan?"

"Yes. The Rinnegan… As power originating from a 'god,' it is only natural for it to be used as a weapon against a 'god.'"

"Then how am I supposed to tell… whether you have deviated from your own 'legitimacy'? You are the reincarnation of a god born with knowledge. I do not believe I can absolutely and precisely determine whether every decision you make deviates from the 'right path' you wish to uphold."

Nagato had no confidence in that whatsoever.

"It is simple. If you discover that among the decisions I make, there is a situation where I grant a certain special group long-term privilege that will not be revoked and that I do not intend to popularize in the future, then there is a high probability that I have deviated from my own 'legitimacy' and should accept correction."

Rei Kaguya narrowed his eyes slightly and said so with a gentle smile.