The lingering ripples of the Blood-Fire Transformation's formation had yet to fully subside. The temperature within the cavern continued to climb. The fissures across the rock walls spidered outward in every direction. From those cracks, orange-red lava seeped forth, oozing slowly down the stone.
Tōtōsai braced himself against the furnace platform, his bulging eyes locked dead onto Shinji. Only after confirming there would be no second eruption did he dare release the breath he'd been holding.
Then he discovered, he'd released that breath far too soon.
The yōki spilling from Shinji's body did not recede. Instead, it continued to change.
The process of the Blood-Fire Change merging into his bloodline was like throwing a red-hot iron ingot into a stagnant pool.
The water boiled but the direction of that boiling was not inward. It was outward. Bone spurs erupted simultaneously from the nodes at his elbows, his shoulder blades, his spine, the overflow points left by the Eighth Transformation.
The white skeletal framework extended, wove, and took shape outside his body at a speed visible to the naked eye. Thunder burst from the gaps in the bones, filling the spaces between the framework, condensing into violet, substantialized muscle. The yōki film expanded outward from his body's surface, wrapping around the entire ever-growing Bone Thunder structure.
This was his Ninth Transformation, the Shura. Manifesting now, without any battle whatsoever.
"Back, back, back, back, back—!" Having already witnessed the fearsome power of this technique, Tōtōsai clutched his iron hammer and scrambled madly toward the depths of the cavern.
His short figure ricocheted twice between the rock walls, his speed rivaling his earlier frantic flight on the fire-ox. Myōga went without saying, that flea simply vanished into the deepest recesses of a crevice. Even his tiny bean eyes could no longer be seen.
A six-meter-tall Bone Thunder Shura rose within the volcanic cavern. The already low ceiling was directly fractured and split open. Chunks of stone rained down from above, bouncing off the Shura Form's skeletal frame and ricocheting away, denting the rock walls with a series of craters.
But Shinji's attention was entirely elsewhere. He was gazing into the interior of the Shura Form. To be precise, he was looking at the position of its chest. That position, in every previous manifestation of the Shura Form, had been empty.
The framework built a ribcage. The thunder filled the thoracic cavity. But that was only form. There was no substance. Like an empty house. It had walls. A roof. A door. But inside, nothing.
Now, within that empty cavity, a light had appeared. A globe of interwoven dark crimson and orange radiance. The size of a fist. Suspended at the very center of the skeletal thorax. It was pulsing. A steady rhythm. A constant frequency. Like a heart. Or rather, it was a heart.
The yōkai-fire that had surged from his blood vessels during the Blood-Fire Transformation's birth, not all of it had remained within his true body. A portion had, following the overflow channels left by the Eighth Transformation, flowed into the external Shura Form structure.
Within the Shura Form's chest, it had spontaneously coalesced into this, a heart. The Shura Form now had a heart.
Shinji stared at that pulsing globe of firelight. The violet veins in his crimson demon eyes flared simultaneously with the orange luminescence. He was not surprised. He was merely pensive, then enlightened. Certain. The path ahead had become clear.
He had, in truth, been pondering a single question: the Ninth Transformation was complete. How then was he to walk the Tenth, the Eleventh, the Twelfth? Though he had already confirmed the principle of accumulating quantitative change to trigger qualitative transformation, he could no longer, as he had before, rely on life-and-death crises to compress and force his own limits.
He understood. To court danger was, sooner or later, to die by danger. What's more, the Essence Shifts of reforging and overflowing could only occur once. They would only ever happen once. The projection, too, could only be cast once. How then to step further? To go further… and turn the shadow, into the real.
This was the reason for his actions in this moment. The source of his current line of thought. Ever adept at synthesis, he had long since realized: the Ninth Transformation, the Shura Form, constructed a second body outside his own, a projection, amplified.
But a projection was still, in the end, only a projection. The Shura Form's skeletal frame might be immensely durable, but it was only bone. The muscle packed by lightning might be thick, but it was only thunder.
The yōki film might be exquisitely sensitive, but it was still only a layer of skin. It had bone. It had flesh. It had skin. But it had no internal organs. No blood. No heart. Just like his own true body, slowly coming back to life, yet not fully alive.
It was an empty shell. A shell that could only be sustained by a continuous, one-way output of yōki from his main body, a shell of immense consumption. This was the fundamental reason the Shura Form could not be maintained for long.
It had no internal circulation of its own. All energy was poured in from the main body, used up as it went, like an hourglass, only ever emptying, never replenishing.
But if the Shura Form had a heart? With a heart, there would be the starting point of a cycle. With a cycle, it could draw in yōki from the outside world to replenish its own consumption. With the ability to sustain itself, the Shura Form would no longer be merely a suit of external armor to be donned and shed. It would be a true second body. He should forge a heart for the Shura Form.
Shinji gazed at that pulsing firelight. The previously somewhat hazy thoughts in his mind now crystallized with a clarity he had never known.
After the heart, naturally, the other organs must follow. The five viscera and six bowels. Corresponding to the Five Elements. The heart belonged to Fire, already present. The liver belonged to Wood. The spleen to Earth. The lungs to Metal. The kidneys to Water. He currently possessed only two elemental transformations, Thunder and Fire.
Fire was now anchored to the heart. Thunder could be anchored to Wood, thunder was born of the heavens, yet struck down upon wood, and from the sundering of wood, fire was born. But it was not yet a perfect fit. Earth, Metal, Water, he still lacked four elements.
But the direction was now clear. This, was the Tenth Transformation that Shinji had now stepped into. Within the Shura Form's thoracic cavity, he would forge the five viscera, one by one. Each completed organ would grant the Shura Form another layer of autonomous circulation, another element to command, equivalent to an ordinary yōkai gaining an additional transformation.
When the five viscera were complete, when the Five Elements were in perfect balance, the internal cycle would be established. That would be the completion of the Tenth Transformation.
For the Eleventh Transformation that followed, Shinji felt it should be the further refinement of this Shura body. He also truly believed that merely having all five viscera and six bowels complete was not yet true perfection. What must be added were the Three Bridges, Heaven, Earth, and Man.
Or rather, they should be called the Three Souls!
Not the Three Souls of the continental traditions across the sea, but something Shinji had deduced himself, synthesizing his own accumulated knowledge with what Kikyō had previously taught him about the workings of this world.
The Heaven Soul governed purity, it could be called the spiritual soul. The Earth Soul governed the impure, the physical, it could also be called the demon soul. The Man Soul governed life and death.
And for this step, Shinji actually possessed an even clearer understanding than he had for the Tenth Transformation. Because he was already a yōkai, his Earth Soul was already abundant. He could already sense the impure energies of the world.
And because he possessed the "Spirit Vision" and "Spiritual Inspiration" granted by the Shikon no Tama, he could perceive the extraordinary within it. More than that, he had a premonition. The Heaven Soul was, in all likelihood, the very ability the Shikon no Tama would grant him upon reaching max Affection.
In other words, as long as he fully completed the Tenth Transformation and forged the five viscera of the Shura, then raised the Shikon no Tama's Affection to its peak, he could directly project his own overflowing Earth Soul onto the Shura Form. Upon that, he would then construct the Heaven Soul bestowed by the Shikon no Tama.
Through this, the intersection of Heaven and Earth would be formed. After that, he would only need to directly comprehend the Man Soul, and this Shura projection would, from the inside out, become truly complete. That would be the Eleventh Transformation.
And beyond that, the final step. To fuse this Shura Form, complete with its five viscera and three souls, back into his own body. Yes. Not to pile on more. Not to expand it. Not to let the exoskeleton collapse and reclaim the energy. True fusion.
To take this second body outside himself, with its complete skeleton, muscles, skin, organs, blood vessels, heartbeat, its fully realized Three Souls, and compress it back within his own form. Merge it into one with his true body. So that his body would truly come alive, no longer driven by yōki, no longer relying on the transformations of blood and bone and thunder merely to simulate the flow of life.
At that point, his body would no longer be the corpse of a demon warrior. It would be a living, breathing, entirely new vessel, reshaped from the inside out by yōki, possessing a complete, self-sustaining cycle of life. Those heart, liver, spleen, lungs, and kidneys, which had been driven and sustained in a mockery of life by yōki, kept from rotting only by constant effort, would truly come alive once more.
From death to life. From demon to ma. Achieving the theoretical apex of Essence Transformation. Perfect quality. The Twelfth Transformation. Possessing a foundation that could touch the threshold of Vaporization, the threshold of Phenomenon. Ready to seek his own Truth.
Such a step-by-step, gradual, cyclical progression, the final achievement would not be low. Even without the Eleventh and Twelfth, a Shinji who had completed the Tenth Transformation would be no lesser than any existence short of a daiyōkai.
At the Eleventh and Twelfth, he would even be confident in wrestling with daiyōkai in their standard humanoid forms. That alone was astonishing enough. After all, theoretically, the "transformations" Shinji gained from fusing with artifacts were all classified under Physical Transformations.
As for why he wouldn't simply forge the five viscera and three souls directly within his own body, but added an extra step of fusion, the reason was the same as before. His true body, at the Physical Transformation stage, could only fuse six transformations.
Only by making additions upon the projection first, could he ultimately perform a "multiplication" upon his true body. Of course, the prerequisite was that all Five Elements must be gathered. Currently, he only possessed Fire. Thunder barely counted as half of Wood.
Once Yura's comb reached max Affection, wind also belonged to Wood, perhaps he could assemble a complete Wood element. It was clear that Shinji still needed to seek out at least three more suitable demon artifacts to fuse.
The road was still long. But at the very least, he had found the path. That was more important than anything.
The Shura Form slowly retracted. The skeletal frame collapsed from the outer layer inward. Thunder scattered into fine motes of light. The six-meter exoskeleton crumbled away completely in the span of a dozen breaths.
But that globe of firelight, the Shura Heart, at the very last moment of collapse, flowed back along the channel of yōki into Shinji's body. It returned to the position of his true heart. Sank deep. Fell dormant. Waiting for the next time it would be awakened.
Shinji opened his eyes. The ceiling of the cavern had split open a great fissure. The light of the sky outside streamed through, casting shifting patterns of light and shadow across his pale face.
He lowered his head. He looked at the Muramasa in his hands. The crack was still there. The dark crimson light still bled across the blade. The sword-soul trembled. It breathed. It waited. One final step. Just one final step. That step was called Will. The heart behind the swing. His Truth.
Shinji tightened his grip on Muramasa's hilt. Then, he sheathed the blade.
Click.
The crisp sound of the sword seating home echoed through the silent cavern.
He knew what he had to do next. Go and gather his Will. Find the reason he swung his blade. The foundation upon which his life stood. For this sword. For the Shura. For himself, to forge that final stroke.