Somehow, Yomi was still clinging to life, even though his chest had completely caved in. Sakura had no idea whether it was due to his skill in Medical Ninjutsu or because of the Mōryō's soul sealed within him, but the malevolent glimmer in his eyes refused to wink out.
"You've guessed correctly, kunoichi…" rasped Yomi. "Miroku and I were once one and the same... but our power was too great… we split apart, and as the years passed, we became known as the Mōryō and the miko… Since then, we've clashed endlessly… each of us striving to prove the worth of our ideals to the other, so that one day, we might reunite as a perfect being, free of contradiction..."
By this point, Yomi was a shell of his former self. The last vestiges that had survived the Mōryō's corruptive presence within him were his obsession with his Thousand-Year Kingdom, which he would never even get to see even if the Mōryō survived the next few minutes.
"What does that mean?" growled Sakura, seizing Yomi's limp body by the neck and yanking him out of the depression in the cave wall. "What happens to Shion if the Mōryō dies!?"
Sakura struggled to grasp the implications of what Yomi had just revealed. If Mōryō and the shrine maiden were truly two sides of the same coin, then what would become of one if the other perished? Would Shion lose her holy powers, or would she die!?
All this time, she'd assumed the demon was simply too powerful, too cockroach-like to die. That was why the shrine maiden of the Land of Demons had always sealed it away, never destroyed it. But what if Miroku had never killed the Mōryō… because she couldn't?
Because doing so would mean her own death!?
The real problem was that Sakura had become entangled with powers she could not possibly understand when she absorbed Shion's breast chakra. Not knowing what would happen to her in turn if the Mōryō died, she hesitated a fraction of a second too long…
"Who do you think you are, Piccolo-daimaō!?" Sakura lampooned. "Whoever you once were, you should have gone to see a psychiatrist instead of cutting away your evil half, you Super Namekian wannabe! Now, you're getting the Mafuba treatment, so enjoy spending the rest of your days in a rice cooker!"
Meanwhile, Shion's sealing ceremony continued unhindered.
"Min, Shin, Gan, Reppyo, Shōzen, Mika, Dan, Raku, Shō!"
As she moved through the hand seals, Shion began to rise, lifting slowly from the ground. The sealing formulae graven into the dais began to glow, banishing the darkness and casting back the orange light of the magma spilling through the crevices around them, as lines of brilliant pink energy linked together, tracing profound runes in the stone platform.
Sakura stepped back warily as Yomi's body suddenly began to wither rapidly, expelling a pillar of dark purple smoke that reeked of brimstone from the gaping hole in his chest.
"Wind Style: Great Breakthrough!"
Careful not to breathe in any of the miasmic smoke, Sakura filled her lungs and cheeks with the cave's hot air and blasted the column of smoke with gale-force winds, but her target somehow remained unaffected.
"What!?" Sakura shouted in shock.
"You fool!" the Mōryō's gleeful voice emanated from the miasma. "Don't you understand? The shrine maiden and I are both spirits born of the Spiritual Plane! Physical attacks are useless unless we've taken on a physical form!"
That being said, even he wouldn't be able to remain in the physical world in soul form for too long.
The pillar of smoke surged towards Shion just as she spoke the final words of the sealing spell. A dome of brilliant energy rose around them, sealing them both inside, while Sakura pounded helplessly against the barrier with her fists.
"Shion!" screamed Sakura. "Lower the barrier!"
The demonic smoke sank into the ground at Shion's feet, and the glowing sealing formulae engraved upon the stone platform flickered and dimmed. The purple forcefield vanished suddenly, causing a startled Sakura to stumble forwards into Shion's arms.
"What have I done…?" groaned Shion, her shoulders trembling with quiet sobs. "If it hadn't been for me, he would never have never breached the seal, no matter how hard he tried…"
…
The miracle the Sage of Six Paths had granted humanity was the power to link their spiritual and physical energies, giving birth to chakra. And yet, those forces had always existed, even before the descent of the Ōtsutsuki.
Overlapping with the physical world lies another layer of reality: the Spiritual Plane, shaped by the collective subconscious of all living things. This world is undeniably real… yet not quite real in the way one might define the word 'real' in a dictionary. This separate, parallel plane of existence wasn't just something Naruto: Shippūden the Movie had completely made up— clues to its existence existed in canon material as well.
For example, when Uchiha clan members use the forbidden technique Izanagi to avoid certain doom at the cost of their Sharingan, they cast a Genjutsu upon the world itself. They wield yin chakra to draw forth the image of a healthy self from this real-yet-imaginary Spiritual Plane, then breathe yang chakra into this image to give it life, effectively getting it to take their place and thus cheating death.
Izanami works much in the same way, except it locks down the Spiritual Plane to prevent an Izanagi user from selecting a destiny advantageous to them from previously infinite possibilities.
The next example is also one of the Sharingan's abilities. The Tsukuyomi is described in the Databooks as representing a 'Spiritual World and Darkness.' Tsukuyomi, Infinite Tsukuyomi, and Limited Tsukuyomi all create illusions by manipulating the Spiritual Plane around their victims to alter their personal realities (albeit on vastly different scales), far surpassing the Genjutsu prowess of your average Kurenai.
In Road to Sakura, an imaginary Sakura is even spat out into the real world when the real Naruto and Sakura are sucked into Obito's miniature Infinite Tsukuyomi, proving the Spiritual Plane's real-yet-fake existence!
Indeed, despite being imaginary, the denizens of the Spiritual Plane go about their lives as usual in these isolated, bubble-like dream worlds— albeit in ways far removed from the physical realm, like a warped mirror casting a distorted reflection of reality.
And finally, the Pure Land where the Sage of Six Paths resides lies within the Spiritual Plane itself, ensuring that for as long as humanity endures, the souls of the fallen have a place to find solace after death. Likewise, the Uzumaki clan's Shinigami is also a denizen of that realm, a soul reaper born of mankind's primal fear of the end.
…
The walls and floor of the cavern began to tremble and crack as a sinister laugh echoed up from the molten depths below. The situation had deteriorated beyond even Sakura's worst fears.
"What's happening, Shion!?" cried Sakura. "Why isn't the seal working!?"
"I don't know!" Shion screamed back at her. "I just used the spell Mother practised the most!"
Shion's mother, Miroku, had never wished for her daughter to follow in her footsteps and so, had never actually taught her anything before her untimely death, forcing Shion to learn in secret by reading her notes and spying on her practising.
The actual sealing spell Miroku regularly used on the Mōryō was entirely different from the one Shion had just used— which was, in fact, the spell used to unseal the demon… which would then allow the shrine maiden to absorb her other self once she was confident she could consume him without falling to corruption, finally becoming a complete being.
"Long ago, a great existence descended upon this land…" Mōryō's disembodied voice echoed through the cavern, rising from the countless crevices that veined the cave floor. "Before their ascension, this transcendent being left behind several artefacts of immense power, scattered across the continent. Perhaps, to a true god, such possessions were so trivial they scarcely even noticed leaving them behind..."
"Run!" bellowed Sakura.
The ground shook so violently that even Sakura struggled to stay on her feet. Stones and boulders rained down around them, shattering the delicate stone arches that spanned the sea of molten magma below.
"In the Land of Demons, one such artefact resonated with the wills of the people," Mōryō's deep, booming voice thundered, shaking the very air itself. "It coalesced their shared despair at a doomed future—hatred of the endless wars consuming their lives and fear that peace would never come. Humankind longed for a saviour and an avenger… and so, from the depths of the Spiritual Plane, I was born: the Mōryō, a demon powerful enough to crush entire armies underfoot..."
Sakura lifted Shion into a princess carry and dashed towards the exit, weaving through falling boulders as the ground crumbled beneath her feet.
"But there can be no darkness without light," Mōryō's voice echoed, almost wistfully, from the depths. "At the moment of my birth, the artefact gathered the people's shared hope for a brighter tomorrow. Humankind yearned for a saviour and a deliverer… and so, from the depths of the Spiritual Plane, Miroku was born: a holy shrine maiden powerful enough to shield them from the horrors of war…"
The cavern was beginning to collapse.
"Thus began our thousand-year battle for dominance, but at last, victory is within my grasp!" the Mōryō laughed. "The hateful Miroku passed on her powers to her powerless daughter along with her foolish dreams of peace for mankind, while my soul has rejoined my true body at last!"
Holding Shion tightly in her arms, Sakura leapt over the widening chasms… but her feet met only formless air as she attempted to land, and together, they plummeted down into the depths.
"I AM REBORN!" the Mōryō roared, his voice seemingly coming from all sides as great tendrils of living shadow burst out of the magma beneath them. "AND NOW, I SHALL BE WHOLE!"