"But I really do have a Sage Body. The fact that I can control these eyes is proof." Nagato pointed to his eyes.
Katsuyu was silent for a moment. "The Rinnegan really is too much for an ordinary person to bear. Your Uzumaki bloodline must be exceptionally pure. But your chakra reserves..."
Katsuyu seemed to think very little of Nagato's chakra reserves.
"Unless there's something wrong with your eyes!" Katsuyu concluded.
"Ah, someone else transplanted them into me," the Asura Path replied.
"Of course. You have red hair, so you're obviously from the Uzumaki Clan. How could you have awakened the Rinnegan yourself?"
Katsuyu seemed amused by Nagato again.
"You figured it out a long time ago?" Nagato was astonished. The Asura Path raised his voice. "Do Mount Myoboku and Ryūchi Cave know, too?"
Katsuyu swayed her dangling antennae, and Nagato felt as if he could sense an emotion coming from her—something called sympathy.
"What did you think? Why else would Mount Myoboku not take your side?"
Nagato: ...
Thinking about it now, no wonder none of the Three Great Sage Regions supported the Akatsuki. They all knew he was a fake. This was really awkward.
It made sense, though. They said the Three Great Sage Regions were ancient places that had existed since Kaguya's era. How could they not know the origins of the Rinnegan? Take Mount Myoboku, for instance. If that bunch of toads believed Nagato had awakened the Rinnegan himself, they would probably have come over to join him as a clan long ago.
"But I didn't expect you to be able to use the power of both Rinnegan with your own strength. When I was in Konoha, I thought your real body couldn't handle the Rinnegan's power, which was why you could only use puppets." As she spoke, Katsuyu climbed onto Nagato's shoulder. "Let me see what's going on with you."
Being able to use the power of both Rinnegan at once proved that Nagato was the third person to bear the identity of the Six Paths. Even by the end of this world, only the Sage of Six Paths, Madara Uchiha, and Nagato had ever managed it. Even Obito Uchiha couldn't do it.
Obito's talent with the eyes was top-tier. When he first awakened them at age twelve, both eyes were already Two-Tomoe Sharingan. The second time, they evolved straight into Mangekyō Sharingan. Not only did his own right eye awaken the Mangekyō, but the left eye implanted in Kakashi's face evolved along with it.
After Obito awakened his Mangekyō Sharingan, the ability dwelling within it, "Kamui," proved exceptionally powerful. It had top-tier space-time abilities, and, more importantly, came with a separate dimension of its own.
That was absurd. This built-in dimension was what allowed Obito's eyes to transcend ordinary Mangekyō Sharingan and reach the level of the divine. In this world, besides Kamui, only Kaguya Otsutsuki's "Amenominaka" came with its own dimension.
The two techniques were, of course, very different. Kaguya Otsutsuki's "Amenominaka" was a Kekkei Mōra she gained after awakening the Rinnegan in her forehead. It was, one could say, the true power of a god in this world. But Obito's Kamui could attack, defend, and move through space-time, and it even possessed the beginnings of a separate dimension like "Amenominaka." It was already close to divine power, the key to opposing Kaguya at the end of this world, and proof of Obito's talent with the Sharingan.
Obito was also highly compatible with Hashirama Cells. The first time he fought using a White Zetsu body, he grasped Wood Release: Cutting Sprigs on his own. Half his body was made up of Hashirama's cells, making him someone who possessed the powers of both the Uchiha and Senju.
Yet even so, Obito couldn't withstand the power of two Rinnegan. He wasn't worthy of being called the fourth Six Paths.
As Obito himself put it: "Just one Rinnegan, with its powerful chakra and ocular power, nearly made me lose myself."
In other words, even at his peak, Obito Uchiha's limit was just one Rinnegan.
Nagato, on the other hand, had both Rinnegan transplanted into him when he was young. Not only could he bear their immense power, he could also remain true to himself. Deep down, he had always longed for peace and wanted only to protect his two friends, Yahiko and Konan.
That was the difference in their talents, and the strength of Nagato's Sage Body.
Katsuyu understood perfectly what it meant for Nagato to use both Rinnegan at once. That was why she began examining his body.
"Both legs are necrotic, and a great many of the pathways in your body are blocked. You've lost vitality, and your lifespan has been severely shortened. Your spiritual energy is weak, and there are signs it's been eroded by foreign spiritual energy for a long time. Most of the cells in your body have lost their vitality after being damaged. Your current, seemingly decent condition is the result of foreign chakra forcibly awakening them..." Katsuyu sounded like a doctor delivering a terminal diagnosis, her voice growing quieter and quieter. "Judging by your body, you were a corpse not long ago, weren't you? How are you still alive? How did you live before? Don't tell me you're a pervert?"
Katsuyu glanced at the Black Receivers on Nagato's body, her meaning clear.
Nagato's eyelids twitched as he listened. Katsuyu seemed a bit sharp-tongued. Using the Asura Path, he said with displeasure, "Why say all that? Can I train in Senjutsu or not?"
Katsuyu thought for a while before answering. "You very likely do have a Sage Body. Otherwise, with your current physical condition, an ordinary person would already be dead. I recommend that you give up the Rinnegan, because its spiritual energy is clearly constantly eroding your body and increasing the burden on it."
"That's not something you need to worry about," the Asura Path said coldly.
"Hmph. It's none of my business. Fine, back to Senjutsu. I already explained the requirements for training in Shikkotsu Forest Senjutsu. First, you need enormous chakra reserves. You don't meet that requirement, but the only reason is your poor physical condition. Once you begin training in Senjutsu, Natural Energy will repair your body and help you meet the chakra requirement, so that won't be a problem. And because your Sage Body has been damaged for a long time, Black Water has a chance to transform your body. You could say you've turned misfortune into a blessing."
Katsuyu paused there, seeming somewhat displeased. "Next is chakra control. The most important thing in Shikkotsu Forest Senjutsu training is learning to maintain balance: between Natural Energy and chakra, and between Natural Energy and the acid. So your chakra control has to be strong enough to maintain both balances. But it can't be too strong, either, because then it'd be easy to expel the acid in the Black Water from your body during training, preventing it from changing your body. Since you can use the Rinnegan, your chakra control can't be weak. And because your Rinnegan were transplanted from someone else, your chakra control can't be stronger than mine, so you can't completely eliminate the acid in the Black Water. So, at a stretch, you meet this requirement, too."
"Why can't I completely eliminate the acid if my chakra control isn't stronger than yours?" Nagato interrupted, puzzled.
"Because the Black Water exists because of me!" Katsuyu replied, then sighed. "If you'd come to Shikkotsu Forest sooner, you might really have become the first person to learn its Senjutsu. What a shame. There are too many Wraiths bound within the Black Water now, and during your Senjutsu training, they'll enter your body along with the energy. Natural Energy is already a violent force, and maintaining the balance between those two energies inside your body throughout your training is incredibly difficult. With so many Wraiths interfering, I really think you should give up."
Before you continue