"Hahaha, I did it!"
By the lake in Shikkotsu Forest, the girl spun in circles holding a person-sized slug.
Faint sunlight filtered through the acid mist, illuminating a diamond-shaped mark on her forehead.
"Mhm mhm, Sakura is truly amazing!"
Katsuyu rubbed the girl's head with its tentacles. Katsuyu also felt a sense of shared glory in her success.
After all, Katsuyu's high-energy cuisine played a part in Sakura mastering the Yin Seal within just a few weeks.
"So, let me prepare a delicious meal to celebrate!" Katsuyu suggested happily.
It wasn't often it caught someone who could appreciate its cooking. Lately, Katsuyu had been enjoying culinary experiments immensely.
Living beings need to find joy in life, and this was especially true for creatures like Katsuyu who had lived for who knows how long.
"Um..." Hearing this, Sakura's expression changed slightly. She quickly set Katsuyu down. "Actually, let's hurry and start the Sage Mode training!"
To be honest, it wasn't that Sakura was picky or disliked Katsuyu's food.
The key issue was that this Katsuyu Sage... is! a! scavenger!
Before Sakura came to Shikkotsu Forest, Katsuyu's daily diet consisted of things like algae, moss, decaying leaves, etc., found in the forest.
After Sakura arrived, to ensure this human also had food to enjoy, Katsuyu directly emulated the ancient Buddha's story of cutting his own flesh to feed an eagle, pulling off a 'cut-flesh-to-feed-Sakura' move!
For the first few weeks, it sent her various salt-baked snails in different ways every day.
It was only because Katsuyu could directly use Sage Mode to create the various substances necessary for human survival that Sakura, after eating snails for weeks, didn't starve to death in Shikkotsu Forest due to malnutrition.
But that taste...
"Alright, you'd better tell me about Sage Mode. I want to be more prepared before attempting it!" To avoid tasting any more slug cuisine prepared by the Katsuyu Sage, Sakura hurriedly changed the subject.
"Sage Mode..." Katsuyu lowered its head, clearing a small space on the ground. "The first step is definitely perception. You need to sense the Natural Energy flowing through all things in the world."
As it spoke, it drew a stick figure on the ground, emitting thread-like sensory tendrils to touch the small spheres of natural energy in the air.
"Mhm, I can sense it." Sakura nodded at it in response.
Using the Wood Release within herself, Sakura could indeed directly perceive the existence of Natural Energy.
Back then, Hashirama most likely also perceived Natural Energy through this method, then studied the Gift of the Hermit Group at Fire Temple to develop his own unique Sage Mode.
This ability of Sakura and Hashirama might be related to both their Wood Release being directly inherited from the God Tree, a weapon.
If Natural Energy were crude oil stored within the planet, then the God Tree was the extraction and processing equipment.
Refining and utilizing the wild, untamed Natural Energy gave rise to the Chakra used by the vast majority of later Ninjas!
"After sensing it, you use it. Utilizing Natural Energy is the innate ability of every living being. It's just that most creatures abandon this ability later on."
The Katsuyu Sage continued drawing. The little stick figure it created plunged into the natural energy-filled lake, drinking the water heartily.
"So, the usage method you're talking about is... eating it?!" Sakura was astonished.
'Although eating is the simplest way for any organism to obtain energy, this kind of Sage Mode... was too wild, wasn't it?'
"Yep. After eating it, awaken that instinct. Then you'll be able to freely control Natural Energy later." Katsuyu stated this as if it were obvious.
There was no need to train the ratio of Natural Energy to chakra like the toads of Mount Myoboku or the snakes of Ryuchi Cave. Just eat and store it, let the body digest it, let the cells adapt.
'No wonder it was called the Celestial Evolution Technique. The whole technique boiled down to survival of the fittest… only those who survive deserve to become sages. Those who can't digest it... well, they die.'
"So, as long as your Holy Land has one contractor who successfully trains, you can later brag to others about a 100% success rate in Sage Mode training, right?" Sakura couldn't help but commented.
Hearing this, Katsuyu laughed heartily, rising up to lean on Sakura's back. "Then you'll have to work hard, aiming to achieve Shikkotsu Forest Sage Mode's breakthrough from zero to one~"
"Sigh, what about application?" Sakura sighed lightly. "Are there any application techniques you need to teach me?"
"What techniques for that? Just stuff Natural Energy into the technique, and you can freely manipulate organic matter on yourself and others, right?" Katsuyu wriggled its body, looking at Sakura with puzzlement.
"Wait, our Sage Mode doesn't need to mix with Chakra?!?!" Sakura's eyes widened, unable to hold back her exclamation.
"Of course it doesn't need mixing. I don't have that thing called Chakra. How could I mix it?"
Katsuyu dispersed its body, then gathered it again, dispersed, gathered. Throughout the process, there wasn't a trace of Chakra on any part of it.
"That's not right. If you don't have Chakra, how did we sign the summoning contract?" Sakura frowned.
She sensed something amiss. She felt she might be very close to Katsuyu's essence, but couldn't pinpoint what was off.
"Just simulate it using the Celestial Evolution Technique." Katsuyu answered nonchalantly.
But this answer struck Sakura's heart like a thunderbolt, connecting all the vague clues.
Chakra was an import brought by the Otsutsuki Clan. The Sage of Six Paths founded Ninshu, sharing Chakra with people.
Essentially, it was implanting that special gene sequence called the Chakra Seed into his disciples' bodies. Then, these disciples branched out across the Ninja World, spreading the Chakra Seed gene everywhere.
And from past records of the Sage of Six Paths training in Sage Mode before his final battle with Kaguya, the three great Holy Lands had mastered Natural Energy far earlier than Chakra's spread.
So, the question arose: these Great Sages had no Chakra. How did they mix with Natural Energy to maintain their Sage Mode stably over the long term?
The answer was clear: they could use Natural Energy to produce their own, inferior version of Chakra!
If the Chakra Seed was seen as a mining tool issued by the 'Otsutsuki Company', then the ore mined would have its surplus value extracted by the company.
These Great Sages of the Holy Lands were like miners using their own pickaxes. Everything they mined belonged to them. They didn't need to heed the mining company's summons. They could even poach its employees right in front of it and intercept the ore they mined.
"I presume you and the other Sages of the three Holy Lands possess reverse-engineering abilities… the ability to revert Chakra back into Natural Energy, right?" Sakura narrowed her eyes. Though phrased as a question, her tone was certain.
On a small scale, this could be a rejection reaction spontaneously born when life encounters foreign energy invasion, or an adaptive evolution to Chakra… a miracle of life!
On a larger scale, they seemed more like weapons evolved through natural selection by the planet to resist being drained by the God Tree and avoid a desolate end… weapons to eliminate the God Tree!
Under Sakura's intense stare, the Katsuyu Sage couldn't hold back any longer, letting out a gentle yet hearty laugh.
"Hehehe, I must say it again, Sakura-chan. Being able to form a contract with you is really... wonderful!!!"