Preparations - Crossover Starting from Ōtsutsuki

As if she had done something utterly trivial, the girl crowned with the title [Demon Buddha Māra] paid it no mind, instead lost in thought.

Around her, the three kings stood silently, keeping their posts.

"Hey, host, are you done playing around?" That familiar lackluster voice reappeared in her mindscape, this time with a hint of urgency. "If you don't find a way to stabilize the passage to the Naruto world, all your earlier arrangements will go to waste."

The girl—no, Satsuki Ōtsutsuki—shifted her awareness into her inner mind and "looked" toward the spatial channel sustained by the Space-Time Medal.

"The Vipralopa's power is too dreadful. It's even affecting the channel's stability. Host, hurry and think of something!"

Satsuki merely cast the reverted system—a glowing orb of light—a look of disdain, and said, "Quiet."

Her consciousness reached into the void and pulled forth a miniature version of the [Atlas].

Without hesitation, she tossed this priceless world-class item into the unstable spatial passage. Through the observation of her golden Tenseigan, she could see the immense changes wrought within the turbulent channel.

Inside, the [Atlas] expanded rapidly, the humanoid statue seeming to come alive. As if conscious, it glanced around the chaotic surroundings.

Enraged by the disorder, it let out a furious roar, raising its hands and stomping down with its feet, as though to anchor itself into the void. By its own strength and through the projection of world will, it firmly stabilized the surrounding chaos. The passage finally began to settle.

Only after finishing this did the colossal [Atlas] return to immobility.

"The result is as expected."

Withdrawing her gaze, Satsuki glanced at the speechless system, her brow furrowed. "Though the channel problem is temporarily solved, my connection with the Giant Tenseigan is unstable. I need to sever ties with this data space quickly."

The system finally snapped out of its stupor, realizing this was its responsibility.

"Uh… uh…" The most hopeless system across all worlds spun nervously in the void, then suddenly bounced excitedly. "Host, I've got it!"

"Speak."

Pff~

Tch. As expected, such was its style.

Behind Satsuki, six purple Vipralopa Truth-Seeking Orbs floated forth~~

Catching her sharp gaze, the system, desperate to survive, quickly said, "It's true, I really do have a method. Host, do you remember the two ways I mentioned to leave this world?"

"I remember." Satsuki's memory was flawless. "You said the first was to let the Space-Time Medal accumulate energy on its own, then wait for it to activate its traversal power again—about three years. The second was to wait until this data world experiences a massive upheaval, then use my power to project the entire world into another real one. That way, you could preserve the strongest data template and act independently."

Her gaze did not waver. "But what does this have to do with stabilizing my link to the Tenseigan?"

"Host, have you forgotten? The Giant Tenseigan was forged by Ōtsutsuki Hamura from all six of his Sage Tools. And the key to the Sage Tools lies in the fact that they each contained the fundamental laws of that world." The system bounced as it spoke. "This world is only virtual, so it contains no such essence. But once you reach another real world and regain freedom of action, obtaining items infused with that world's laws will be easy for you."

"And then?"

"Then, host, you only need to toss those items through this spatial passage. The Giant Tenseigan will automatically absorb them, amplifying its signal. That way, not only will its power grow stronger, but your connection with it will become stable. Even across multiple worlds, you could borrow its strength at will."

After hearing the explanation, Satsuki pondered. The system's words did seem plausible… but really, with this system's level of intelligence, could it have come up with such an idea?

Seeing her gaze, the system bounced irritably. "Host, are you doubting the ability of The Strongest System Across All Worlds again?"

Tch… forget it.

There was no need to dwell on such trivial matters. Satsuki withdrew her consciousness from the mindscape and returned to her body—in reality, only an instant had passed.

"Back to the Sixth Heaven."

With a command to the three kings who bowed respectfully, her figure flickered and returned to her original seat in Tāvatimsa Heaven.

With all players expelled from the dungeon "Six Heavens of Desire," the entire instance was reset. The once-ruined Tāvatimsa Heaven restored itself to its pristine state.

Once more, countless "Demon Buddha Worshippers" and grotesque elite monsters populated the endless land.

Disgust flickered in her eyes as she looked at the noisy NPCs that surrounded her, chanting incessantly. With a sweep of her palm, gray Vipralopa energy erased them like ink wiped from a scroll, reducing them to nothingness.

Sensing her wrath, the NPC mobs shrieked and scattered. After a few minutes, at last, the Sixth Heaven regained some quiet.

Seated upon a black mandala, Satsuki gazed at the three kings she now controlled with her advanced "Wheel of Heaven Reincarnation." Their silence and composure pleased her.

"From now on, this one wishes no disturbances. Furthermore, this one has a task for you."

"Your command, my lady."

"Phantom Spirit King, you possess the authority of [Status Infusion]. Great Brahma King, you wield [Energy Control]. I require the two of you to construct a formation that spreads the effect of the Brahma Chant throughout this entire world."

With a wave of her hand, a graceful figure appeared behind the three kings—it was the NPC [Gandharva], who had appeared once before.

Bound by her limited AI, Gandharva pressed her palms together reverently before Satsuki and the three kings. "Anantavata."

Ignoring the NPC's scripted actions, Satsuki continued: "Her Brahma Chant is powerful. But this one has no need of endless followers—that would only bring displeasure. Simply ensure that all who hear it completely forget anything concerning us. Nothing more."

"By your will." ×2

The Phantom Spirit King and Great Brahma King immediately departed with Gandharva to prepare the formation.

Meanwhile, the Wheel Yama King remained at Satsuki's side, his mood sour. He could not shake the shame of his avatar being defeated by the invaders, especially when the Demon Buddha awakened.

It was not that he lacked power. His pure combat authority of [Instant Death] could even evolve into the supreme [Super Instant Death], and he had once been the greatest pressure on Satsuki when she could not yet fully control the Demon Buddha. But arranging formations was far from his specialty, leaving him unsettled.

Naturally, Satsuki noticed.

"Yama King."

"My lady, your servant is here."

"Your value differs from theirs. You need not be troubled by my arrangements."

"…Yes, my lady. I understand."

Her next words tore open his wound without mercy: "As for your avatar's defeat—failure is failure. This one will not accept excuses or justifications."

Her words struck him like a heavy blow. His crimson head bowed low, trembling, unable to meet her gaze.

"But this one has always believed: strength and weakness are not absolutes, but relative. You, blinded by pride, failed to see this truth."

With a gesture, Satsuki lifted his head from afar, forcing him to meet her eyes.

"This one desires that you recognize the reason for your failure, not wallow in despair. Remember—this one can tolerate failure, but not stupidity."

From that day onward, under Satsuki's orders, the entire dungeon Six Heavens of Desire was soon filled with the effect of the "Brahma Chant."

Any player or GM who stepped into its range would instantly forget their original purpose and be randomly teleported to another map.

As time passed, what had once been a hot topic of raiding was swiftly forgotten within days. Even the official website announcements were replaced.

No one remembered that an End-Tier dungeon had ever existed, waiting for players to challenge it. All they knew was that the game would shut down one year later.

...

One year later

Only 35 minutes remained until the shutdown of YGGDRASIL.

Great Tomb of Nazarick, Underground

So happy… truly… so very happy…

Momonga sat silently upon his throne, immersed in memories of the past.

The system interface before his eyes remained unchanged, as familiar as ever.

The clock read 22:24:01, then ticked forward.

His quiet reverie was suddenly broken by a familiar voice in the corner of his interface, stirring waves in his heart.

"It's been a long time, hasn't it, Momonga-san?"

Momonga turned his gaze. At the other end of the grand, ornate white round table sat a black slime utterly mismatched with its surroundings.

"To be honest, I never thought you'd come, Herohero-san." Joy was evident in Momonga's voice. Though today was the game's final day, he was not alone.

"It's been nearly a year since we last met, hasn't it?"

The black slime's features showed exhaustion, but he still answered seriously. "It's been that long, huh. I still remember back then—I suddenly had to take several days off for no reason, and my boss chewed me out. Hahaha."

"Yeah…" Momonga replied wistfully. "That was probably the last time our guild managed to gather. I've already forgotten why, but it must have been for some great goal."

"I don't remember clearly either. Just that because of those days off, my boss kept piling overtime on me. Lately my sense of time is all messed up."

Uh…

Hearing this, Momonga grew worried about his comrade's health. "Herohero-san, isn't your situation pretty serious then?"

The black slime spread his hands. "You mean my body? Of course it's exhausted. It feels like my special ability is dragging me down along with it."

He seemed embarrassed. "Sorry, Momonga-san, I just keep complaining."

"Don't worry about it." Momonga quickly raised his hand with a smiling emote.

Herohero glanced at the clock, speaking wearily: "I need to log off."

With that, he tapped the system window with a soft hand.

"Oh…" Momonga's words caught for a moment, then he chose to properly send off his final companion. "Please rest well."

Before logging off, Herohero's hollow eyes swept around nostalgically.

"Still, I didn't expect Nazarick to still exist. The guild upkeep costs must be no small sum."

"Eh?" Momonga blinked.

"As guildmaster, you've kept it going all this time."

Even as an undead, Momonga could feel the gratitude in Herohero's tone.

"Well, Nazarick is the stronghold we all built together. It's the fruit of everyone's efforts. Of course I'll take good care of it."

Herohero tilted his head. "Momonga-san, you've really worked hard. If fate allows, let's meet again someday."

With that, he pressed the logout button, and his slime avatar vanished into light.

A system notification appeared: [Guild member Herohero has logged out.]

Leaning back into his ornate throne, Momonga sighed, then steadied himself. In a voice pretending his comrades were still there, he spoke into the empty air:

"Today marks the end of YGGDRASIL. A rare chance—why don't we stay together until the very last moment…"

The more Momonga spoke, the heavier his tone became. The empty throne hall around him silently echoed a cruel truth: now, the Great Tomb of Nazarick was home to only him.

After today, as working adults, everyone would likely have no "fate" to meet again.

...

Meanwhile, in the Sixth Heaven of Desire—

Satsuki fixed her full attention on the countdown timer the system displayed.

Since in-game time did not match real-world time, she had ordered the system to gather this information. With it, she could ensure no accident occurred during the world transfer.

As the clock drew closer to midnight—

Satsuki began stirring the Vipralopa power within her body while also activating the Space-Time Medal's accumulated energy. Instantly, the entire Sixth Heaven fell into chaos. Apart from the three kings, protected by authority-level power, every monster on every floor was caught in the distorted time-space force, turning to stone before crumbling into dust and scattering.

Satsuki remained in her usual reclining posture atop the black mandala. Above her, the clouds and sky twisted violently under the tremendous power. Thunder rumbled and spread through the warped space-time, and the earth itself groaned as if on the verge of collapse.