Earth's Saviour is the Heavenly Demon

Ashen steeled himself, his consciousness diving deep into Eren's core. He visualized the meridians as a sprawling network of rivers, their paths blocked by debris. 

Instead of clearing each obstruction, he imagined carving out a single, crude channel that bypassed the worst of the blockages.

"It won't be elegant," he muttered to himself, his thoughts sharp with determination. "But survival isn't about elegance."

Ashen's consciousness moved with surgical precision, guiding threads of energy through Eren's body. He began with the central meridian, using the faintest trickle of qi to test the waters. 

As expected, the energy resisted, straining against the constraints of the twisted pathways. Ashen gritted his teeth, his focus unyielding as he forced the energy to move.

Slowly, he carved out the first loop, a crude but functional reservoir. The energy pooled there, swirling chaotically before settling into a tentative rhythm. Ashen repeated the process twice more, creating the remaining loops and linking them into a fragile chain.

The energy flow stabilized, if only slightly. But the real challenge was yet to come.

Ashen's consciousness dove into the central loop, gathering the chaotic energy into a single point. The compression was agonizingly slow, each strand of energy resisting his control. 

Sweat beaded on his brow as he forced the threads together, his will bending the chaotic current into submission.

The makeshift dantian formed a glowing nexus of energy within Eren's lower abdomen. From there, Ashen began to disperse the energy, guiding it through the stabilized pathways in thin, controlled streams.

Hours passed as Ashen painstakingly extended this rudimentary circulation system. Each step was a battle, the energy threatening to break free and flood Eren's body with uncontrolled power. Sweat dripped down his face, his breathing labored as he pushed his consciousness to its limits.

Finally, the qi began to circulate, however faintly, through the makeshift pathway. Relief washed over him as the oppressive heat within the body began to dissipate. The energy, though weak, was moving.

Ashen's consciousness wavered like a candle in a storm. The makeshift qi circulation system he had forged was holding, if only barely. 

The chaotic yang energy that had threatened to incinerate Eren's body now flowed sluggishly through the crude channels he had carved. But the battle was far from over and his relief short-lived.

Unbeknownst to him, the circulation he had established was triggering an unintended side effect. The faint trickle of qi began to seep into Eren's broken bones and torn muscles, accelerating their healing at an unnatural pace. What should have taken months was happening in mere moments.

The pain was excruciating.

Ashen's mind reeled as the body convulsed, a surge of agony rippling through his consciousness. He hadn't accounted for the Heavenly Yang Constitution's regenerative properties, which were now being amplified by the circulating qi. Each broken bone that mended, each torn muscle that knit itself back together, drained the body's already meager energy reserves.

"This isn't right," Ashen thought, panic rising as he felt the body's strength waning. "It's healing too fast... it's killing itself."

"This damned constitution," he thought bitterly, his vision blurring as his strength ebbed away. "It heals even as it destroys."

Every broken bone that mended, every torn muscle that stitched itself together, came at a catastrophic cost.

The rapid regeneration wasn't a miracle; it was a ravenous force, devouring what little energy remained in the body. Ashen could feel life slipping away with each passing second.

The constitution was both a gift and a curse. It worked tirelessly to repair, yet its very nature threatened to push Eren's fragile body to the brink.

Ashen's vision blurred, his strength faltering as he struggled to maintain control. The balance he had fought so hard to achieve was slipping away.

He tried to regain control, to slow the flow of energy, but it was too late. The body's instinctual response to the yang energy had taken over, driving the healing process to its limit. The same force that was mending Eren's body was also draining him of life.

The oppressive heat that had once filled the room had subsided, replaced by a pervasive warmth that seeped into every fiber of Eren's body. Yet, Ashen's relief was not fleeting. He already had an unresolved crisis, yet he was faced with another.

The circulation system he had painstakingly crafted was holding the energy at bay, but the excess yang still pooled dangerously in one place: Eren's swollen, throbbing phallus.

The bulging heat radiating from it was like a pressure cooker on the verge of exploding. If left unresolved, it would undoubtedly lead to permanent damage, undoing all the progress Ashen had made.

But his body was giving out. His mind screamed for him to act, to channel the energy elsewhere, but the mounting exhaustion dulled his senses. Every breath felt like a mountain pressing against his chest. His thoughts grew sluggish, his control slipping.

"No... not yet," Ashen muttered, his voice barely a whisper. "I've come too far... to fail now."

The room spun as his body reached its limit. Ashen felt himself falling, his legs giving out beneath him. A sharp, metallic taste filled his mouth as his consciousness teetered on the edge of oblivion.

With a resounding thud, his body hit the floor. The sound echoed through the silent room, a final punctuation to his desperate struggle.

For a moment, there was only darkness. The faint hum of circulating qi was the only reminder that he had succeeded in averting the immediate crisis. But the victory felt hollow.

The unresolved yang energy still burned, and Ashen's tenuous hold on consciousness was slipping through his fingers.

The creak of a door jolted his fading senses. The sound was faint, almost imperceptible, but it cut through the haze like a dagger.

Through the dim light of the room, a shadowy figure slipped inside. The silhouette moved with quiet, deliberate steps, the faint rustle of fabric accompanying their movement.

Ashen's blurred vision caught the outline of the intruder as they drew closer. A black silhouette loomed over his prone form, their features obscured by the dim light.

"Who..." he tried to speak, but his voice was nothing more than a hoarse whisper. The last threads of his strength unraveled as his consciousness slipped away, leaving him at the mercy of the unknown figure.