The Boundary

To the north of Heian-kyo, at the foot of the rolling Mount Hiei, a vast and majestic spiritual power gathered through the ley lines at the Black Tortoise Altar hidden within the mountains. It then transformed into a thick pillar of energy that burst through the heavy layers of rock. The azure pillar of spiritual energy shot straight into the clouds, causing the sky to darken under its sheer force. The earth trembled slightly, and every creature in Heian-kyo and its surroundings—whether they possessed spiritual vision or not—sensed this immense power and turned their gaze toward it.

"W-what's going on!? What the hell is this massive spiritual power!" A drunken tanuki was jolted awake by the sudden surge of energy, his intoxication instantly vanishing. He, along with other humans and yokai, rushed into Seimei's courtyard, all staring in astonishment at the distant pillar of spiritual energy.

"This is the Four Symbols Corresponding Grand Array! Has a Divine General activated the Four Symbols Array?" Nura Rihyon frowned at the sight, then immediately turned his gaze toward Yura, who looked equally stunned.

"Hey! Why would a Four Symbols Array suddenly activate? Explain yourself, Onmyoji!"

"I don't know! That's the Black Tortoise Array of the north, but the Black Tortoise Seal was lost over twenty years ago! The Onmyoryo hasn't had a Black Tortoise Divine General for a long time!" Yura scratched her head in frustration, the situation completely exceeding her expectations.

"Lord Seimei! This power is..."

"Yes, it is the Four Symbols Array of Heian-kyo, the power I once wielded." Seimei stroked his forehead and spoke softly. At this moment, his Azure Dragon Seal was under Miketsu's safekeeping.

"..." Kagura stared blankly at the distant pillar of spiritual energy, her thoughts unknown.

"Damn it, who could be activating the Black Tortoise Seal? Didn't the previous Black Tortoise Divine General, Master Enmi, already die? Hey, Hao, what should we—? Huh? Hao?" Yura looked around in a panic but couldn't find Miketsu anywhere. She suddenly looked up at the sky and saw a streak of light flying rapidly toward the pillar of spiritual energy.

Miketsu manifested her Celestial Maiden power and streaked through the sky at high speed, heading toward Mount Hiei in the north of Heian-kyo. She soon reached the source of the spiritual pillar—a massive hole torn into the mountainside.

Without hesitation, she dove into the cave through the edge of the spiritual pillar. Inside the mountain, she saw the glowing Black Tortoise Altar. With a flick of her sleeve, countless paper cranes flew out, swarming the altar. Following a series of explosions, the Black Tortoise Altar was buried in dust. The soaring pillar of spiritual energy twisted and gradually shrank until it vanished.

"Phew... that's all I can do. I wonder how much actually escaped?" Miketsu exhaled slowly, speaking to herself. She then flew out of the cave and looked up at the sky, tracing the lingering trail of the spiritual pillar. As the trail reached its highest point, it veered in one direction. It was clear that the massive spiritual power that had leaked from the Black Tortoise Seal had all headed that way.

"The east?" Looking at the mountains to the east, Miketsu narrowed her eyes and murmured solemnly.

"Just what are you trying to do, Nine-Tailed Yokai Fox..."

...

In a vast, eerie underground space, countless foxfires floating in mid-air illuminated the surroundings. This was no natural cave, but an underground ruin built by hand.

The floor was paved with simple, flat stone slabs. Though riddled with cracks, it remained relatively level. Numerous pillars stood in concentric circles, spreading outward. Many of them had snapped and fallen. The surrounding stone walls were engraved with blurred murals, most of which were shattered, with soil spilling through the gaps. Vines and weeds encroached upon various parts of the ruins, and scattered human remains could be seen everywhere.

In the center of the ruins, within the innermost circle of stone pillars, a massive abstract image of a butterfly was carved into the floor.

Above this abstract carving, a translucent monk sat in mid-air, chanting scriptures with his hands pressed together. Above him was a sphere of spiritual energy glowing with an azure light. At the center of the sphere floated the rotating Black Tortoise Seal. At the top of the ruins was a skylight leading outside, through which a torrent of spiritual energy poured down, feeding into the sphere. The continuous flow made the spiritual sphere grow brighter and brighter.

Standing not far from the sphere, Tamamo-no-Mae watched the scene in silence.

Suddenly, the spiritual energy pouring in from the skylight dwindled and eventually vanished entirely. The monk sitting beneath the sphere opened his eyes and looked at Tamamo-no-Mae, speaking respectfully.

"Lord Tamamo-no-Mae, the spiritual energy transmission from the Black Tortoise Array has been forcibly interrupted."

"They reacted quite quickly. So, how much did we get?" Tamamo-no-Mae spoke in that deep, androgynous voice. The monk named Enmi replied, "About eighty percent."

"Eighty percent? Heh... that is enough." Gazing at the azure sphere containing terrifying spiritual power, Tamamo-no-Mae looked up slightly. After a pause, they spoke to the void.

"The preparations are complete. It is time for you to show yourself, Yakumo Yukari!"

"Ara ara~ Don't be in such a rush~"

Accompanied by a playful, mature female voice from the void, a gap tore open in space. A beautiful yokai woman with a languid expression stepped out slowly.

She had long, slightly curly blonde hair and deep, enchanting purple eyes. She wore a striking and somewhat strange taoist robe embroidered with the Taiji and Bagua patterns, over a voluminous long skirt. Her left hand held a closed paper umbrella, while her right hand was raised as she let out a yawn.

"Uwaaa~ I thought you'd take a bit longer, so I took a little nap. I didn't expect you to be so fast~"

"The reaction speed from Heian-kyo was somewhat unexpected. We couldn't completely drain the spiritual power, but it doesn't matter. What we have here is enough," Tamamo-no-Mae said in a low, steady voice, looking at the yokai woman named Yakumo Yukari.

"Heian-kyo? I have indeed heard that many extraordinary people have appeared there recently. Hehe... how interesting. The world seems to have changed quite a bit while I was asleep. I never imagined the day would come when you would seek me out for cooperation~" With a playful smile, Yakumo Yukari looked at Tamamo-no-Mae.

"Enough. There will be plenty of time for chatter later. Let us finish the business at hand, Great Sage."

"Yes, yes~ You're becoming more and more boring. I warned you long ago not to pour your emotions into humans. Look at you now..."

"Yakumo Yukari..."

"Alright, alright. Put your tails away. I'll start now, okay?"

After calming the nearly hostile Tamamo-no-Mae, Yakumo Yukari shrugged slightly. She then turned her gaze toward the center of the ruins, focusing on the massive floating sphere of spiritual power.

"Such an immense amount of spiritual power. This is quite a project, but I can handle it."

Yakumo Yukari smiled faintly, then raised her paper umbrella and pointed it at the spiritual sphere.

"The Boundary between Humans and Yokai!"

A purple light shot from Yakumo Yukari's umbrella, striking the azure sphere. Starting from the very bottom, a rising 'mirror surface' began to form. The azure spiritual energy filtered through this 'mirror surface' rapidly turned purple, transforming into eerie demonic energy.

Under Yakumo Yukari's power, the nature of the Black Tortoise spiritual power was slowly being altered.