"Alright, I'll give it a try. I'm curious about this immortal power too."
Uchiha Retsu nodded, then closed his eyes and focused on sensing the natural energy drifting in the surroundings.
In the ninja world, chakra is formed in the lower dantian and flows through the meridians. It isn't stored permanently; instead, however much you need is synthesized on the spot from physical and spiritual energy.
To put it simply, it's like a flame constantly burning in the lower dantian. The bigger the fire you want, the more firewood you must add—your physical and spiritual energy being that firewood.
This was also why Sage Mode had a time limit. Once the senjutsu chakra—formed by fusing newly generated chakra with natural energy—was used up, it was gone. You had to gather and fuse it again.
Spiritual power, on the other hand, was born in the upper dantian, within the sea of consciousness. It was closely tied to the soul and existed continuously. When consumed, it recovered slowly over time. The way the two energies were generated and stored was completely different.
At this moment, within his sea of consciousness floated a faint cluster of white light—his newly cultivated spiritual power.
Although this was his first time manipulating it, his long experience in controlling chakra allowed him to guide it with surprising precision. The small cluster of spiritual power flowed smoothly through his body.
Following the route described in The Blood Sacrifice Wood-Nourishing Art, he guided the spiritual power through his meridians while drawing natural energy into his body.
Carefully, he fused the two according to the proportions recorded in the manual, then circulated the merged energy along a fixed pathway. During the process, natural energy and spiritual power gradually intertwined.
His first attempt failed. Unfamiliar with the route, the freshly fused energy scattered halfway through, and the natural energy returned to the world.
But Retsu didn't get discouraged.
Again and again, he absorbed natural energy, merged it with spiritual power, circulated it, and adjusted through trial and error.
After several failures, he finally succeeded in guiding the fused energy through the entire pathway, allowing it to complete the full circulation and flow into the middle dantian at his chest.
The moment it entered the middle dantian, spiritual power and natural energy fully merged, giving birth to an entirely new kind of energy.
It carried the purity of spiritual power and the vitality of natural energy. Its aura was unique.
As soon as this new energy formed, it spread like mist through his meridians.
Retsu understood instantly—this was the immortal power recorded in the manual.
Even more fascinating, as the immortal power circulated within him, it began gently nourishing his body. Meanwhile, natural energy in the environment started flowing into him on its own, slowly replenishing what was consumed, forming a faint cycle.
Retsu couldn't help but admire the creator of this technique.
They had essentially figured out how to cultivate a human like a demon.
From his observations, most humanoid demons—including fully human-looking ones like Xia Lan, or even half-demons like Inuyasha—had demonic energy spread throughout their bodies, but its core was located in the middle dantian at the chest.
The immortal power described in the manual was likewise stored in the middle dantian.
Retsu slowly opened his eyes and clenched his fist.
He could clearly feel his body slightly strengthened, his physical power subtly enhanced. However, because his spiritual power was weak, the immortal power he had generated was thin. The improvement was minimal.
"Did it work?" Kikyo stepped forward eagerly, her eyes filled with anticipation.
"It worked." Retsu nodded, then sighed helplessly. "But my spiritual power is too weak. The immortal power it produced is pitifully small. I'll have to accumulate it slowly over time."
"That's already impressive!" Kikyo praised sincerely, then her expression turned concerned. "Does it affect your spiritual power itself?"
Clearly, she was worried whether immortal power might damage the foundation of spiritual power.
Retsu carefully examined the spiritual power in his sea of consciousness.
"It does consume spiritual power during the fusion process, but it's already recovering naturally. There's no lasting damage.
Spiritual power acts more like a 'medium' for converting immortal power. Once the conversion is complete, immortal power sustains itself by absorbing natural energy. It doesn't continuously drain spiritual power."
"So the strength of one's spiritual power determines the cultivation speed of immortal power?"
Retsu suddenly looked at Kikyo, his eyes lighting up.
"For someone like you, with such powerful spiritual power, as long as your body can withstand the circulation, you'll cultivate immortal power extremely fast!"
"Kikyo, you're practically a genius for this!"
Kikyo's cheeks flushed faintly. Though she tried to remain composed, a smile tugged at her lips.
"I can't even properly circulate natural energy in my body yet. Calling me a genius is too soon. And the manual clearly states that the meridians have limits. You can't recklessly increase the flow."
Even so, the slight upward curve of her lips betrayed her satisfaction.
Several days later, Kikyo suddenly opened her eyes.
A bright radiance flashed within them, and a genuine smile spread across her face.
"Retsu, I've cultivated immortal power too!"
Retsu had already sensed the change in her energy, but he deliberately teased her.
"Congratulations, Immortal Kikyo!"
"What kind of name is that? It sounds terrible." She couldn't help but retort.
Then she frowned slightly.
"Unfortunately, we were too optimistic. Even though my spiritual power is abundant, the amount of natural energy I can stably absorb each time is tiny. My progress isn't nearly as fast as we imagined."
"Don't rush. Just keep practicing. We've got plenty of time," Retsu reassured her.
He found it rather amusing.
Kikyo was extraordinarily gifted in spiritual power, yet despite her earlier ease in sensing natural energy, she struggled when it came to absorption and fusion.
He was the exact opposite.
He could manipulate natural energy effortlessly, but his progress was limited by his weak spiritual power.
They complemented each other perfectly.
"No matter what, we've mastered immortal power. That's worth celebrating."
Retsu suddenly changed the topic.
"Kikyo, do you know how to use a sword?"
"Hm? No. Why are you asking all of a sudden?" she replied, puzzled.
"How about I teach you?" he suggested eagerly.
"Why do I suddenly need to learn swordsmanship?"
"Nothing wrong with picking up another skill. We've got time anyway," he insisted.
Though she didn't understand his sudden enthusiasm, Kikyo eventually nodded when she saw the hopeful look in his eyes.
"Alright."
"Great!"
Retsu beamed. A swirl of space twisted open as he activated Kamui. Two wooden chests fell out and landed heavily on the ground.
He glanced at them, then pushed one toward Kikyo.
"Go change first. That one's for you."
He lifted the other chest. "This one's mine."
"Change clothes?" Kikyo narrowed her eyes. "You planned this in advance, didn't you?"
"Heh. Of course!" Retsu admitted shamelessly. "Hurry up. I'll wait outside."
Without giving her a chance to refuse, he carried his chest into his room.
Kikyo looked at the chest in front of her and curiously opened it.
Inside was a beautifully crafted set of women's samurai armor, complete with undergarments—and beside them lay an exquisite katana.
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