"Ahh, that's it, huh... You actually mean that without Natural energy, I have zero chances of evolving Sharingan into Rinnegan, but with Senjutsu Chakra, I have some chances, but can't be sure!" asked Kakashi, feeling a little hopeful, since he already decided, that he will learn Senjutsu later on anyway.
And if that can really help him in even making his Chakra Potent enough for evolving Sharingan into Rinnegan, then that would be an even better outcome.
[Affirmation. Simply having vast chakra reserves, can't evolve even Eternal Mangekyō Sharingan into Rinnegan. The answer always remains "NO"]
[Like the case, where even if Host has higher Chakra Reserves than any Ōtsutsuki's later, still wouldn't get Ōtsutsuki's Bloodline, just gain some similar traits, but for Bloodline, the answer is also a definite "NO", the same is the way with gaining Rinnegan with vast chakra alone.]
[However Natural energy makes things different. Because at one point, Rinnegan is actually derived from Life Force and Natural energy of planet earth, that is absorbed and integrated by the God Tree.]
[That God Tree later produces, the Chakra Fruit. With Kaguya Ōtsutsuki consumes it and gains Rinn-Sharingan other abilities. Later she with Yin-Yang Release, but also in a human way, gives birth to her sons, Hagoromo Ōtsutsuki and Hamura Ōtsutsuki, both inherited their powers from Prime Kaguya Ōtsutsuki.]
[Hagoromo Ōtsutsuki, who has gained dōjutsu, the Rinnegan, in one sense, gained it through a perfected form of all three energies, physical and spiritual energies, which are Life Force of the planet, and Natural Energy.]
[So, Host, who will eventually have vast chakra reserves, learns Sennin Mode, combining these three energies, may evolve Sharingan into Rinnegan. However, that's still can't be said with accurate way.]
[Since, Host or any Shinobi, can only absorb Natural Energy to temporarily enter Sennin Mode, but unlike God Tree, they can't permanently integrate it.]
[Host would need continuous practice and use of Sennin Mode, to have these three energies together, and make his Chakra more Potent but if it still be successful, can't be sure.]
After hearing this, Kakashi contemplated it all, and remained silent for a few minutes, nodded and muttered, "Even If it succeeded or not, I am definitely going to learn Sage Mode."
[D... Does Host have any other queries?]
Kakashi looked at the system, thought for a bit, but couldn't think of anything, heck even these information he has gotten still needs time to process and understand for him. He shook his head and said, "No, nothing comes in my mind for now."
[Very well then...]
Kakashi tilted his head, looked at the transparent status screen in front of him, but not the dialogue box beside it. "Is it really gone, hello, system, are you there?" Getting no response, Kakashi shrugged, understanding that the system really gone, leaving only the status panel interface alone.
[Host: Kakashi Hatake]
[Chakra Pool: 1,005,350/1,007,890]
[Chakra Control: 92/100]
[Chakra Level: Peak-Kage]
[Chakra Affinity: All]
[Chakra Growth: +50,000 per day]
"Ha, 50,000 huh," chuckled Kakashi and muttered, "Wait! I should have asked it, when will be the next and final upgradation comes? Tch.. well I can't ask it now."
Kakashi shrugged it off, and started to contemplate about all the information he has gotten today or tonight, just now.
________________________________
Two days passed.
It's morning time, and Kakashi was summoned by Hiruzen, and currently stood in front of Hiruzen, in the Hokage's office. While Hiruzen, sat on his chair, taking a drag from his smoking pipe, and a document in his hand.
But they both weren't alone, behind Hiruzen, stood a young man, with ink black eyes, long dark brown hair, tied in a lower ponytail, wearing light grey pants, a green shirt, and Shinobi sandals. He also wore a forehead protector, however not of Leaf Village.
"Kakashi, he is the current leader of Village Hidden in the Waterfall, Shibuki." said Hiruzen, pointing at the young man behind his right, who warily nodded to Kakashi, then looked around the Hokage office with a startled and panicked look in his eyes, like someone was about to attack him. Kakashi looked at Shibuki and then back again at Hiruzen.
"He requested a C-rank escort mission, and I assigned it to your team, to escort him back to Land of Waterfall, Takigakure Village safely." explained Hiruzen to Kakashi, while also passing the mission details document to him.
Kakashi read the mission details, then looked at Shibuki and thought, 'Huh? So he is Shibuki, current leader of Waterfall Village after the death of previous leader, Hisen. But he looked like... a coward. Is he really a leader, and where is his guards.'
'Takigakure, despite being a small village, isn't exactly a poor village, and has better resources than even Sunagakure, in some ways. Moreover, I thought after Land of Waves mission, there was directly Chūnin exams, was there really another mission for Team 7 in canon?'
________________________________
A few days back, in another location, Land of Rain, Village Amegakure.
In the village, a colossal building, a tower of a high-tech fortress of a kind. At the highest point of the tower room, were present four figures, one was a frail-looking man, sat on a large mechanical chair, with two immense metal rods extending from its back.
This was Nagato Uzumaki, his hair was dull red, face gaunt, but the Rinnegan in his eyes were unblinking, gazing ahead with immense power. Beside him stood, a woman with blue hair, pulled back, a paper ornament tucked in it. Wearing a high collared, black robe with red clouds design, this was Konan.
Another orange-haired figure stood, with many black receivers in his body, a vacant, lifeless puppet of Yahiko, controlled by Nagato, having similar Rinnegan design in it's eyes, not real though but the fake one.
They were looking at the back of the fourth figure, who also wears a dark robe, with red clouds design on it. Wearing a spiral orange mask, with a single eyehole of his was all visible.
"Madara, what happened? Why did you stop talking suddenly?" asked Nagato, in deep, intimidating voice.
"Nothing." answered Obito, simply without looking back, disguising himself as Madara in front of others. He was looking at the outside, the unending rain of the Land of Rain, continued its ceaseless downpour.
'There was a minor fluctuation in my Kamui dimension, like someone entered it and gone instantly,' thought Obito, crossed his arms. 'The only person besides me, who can enter in Kamui without problem should be only... Kakashi, who has my left Sharingan eye.'
Obito chuckled, but his expressions hidden under his mask and thought, 'Does that mean, he finally able to use its true form, Mangekyō? Ha... Interesting!'