Date A Live: Starting as Acheron

"We'll only get one shot at this, so make it count. How do you want to do it? Keep it quiet, or make it loud?" Kyo asked. Currently, the two were hiding in the lush outskirts of the island, which DEM had, for some reason, left untouched.

"My my, did you already forget my specialty? With [Zafkiel], we could redo this as many times as I please." Kurumi smiled. "Maybe this is actually our hundredth attempt together?"

Kyo felt a cold sweat on the back of his neck. "Don't joke at a time like this. If you don't want to choose, then I say we're doing a stealth run. The escape route will be your shadow travel ability."

"And what is your plan if we're discovered before then?" Kurumi asked smilingly as she faded into Kyo's shadow.

"We're two personified walking natural disasters. I think we'll be fine." Kyo frowned. "That's a flag, isn't it. Fudge. Change of plans, Kurumi; we're working out a few more contingency plans."

——————I am the dividing line that skips time——————

Kyo silently traversed the spotless metallic corridors of the Neryl Island Westcott Organization's underground island headquarters. After having the good fortune of meeting a researcher returning to work after getting some fresh air, Kyo easily slipped into the building by following behind them. With [White] active, the researcher didn't register his existence at all. 

Clutching [Origin] closely, Kyo slowly navigated through a maze of off-white hallways covered in various labeled doors. From a glance, Kyo could read "Weapons Testing", "Spirit-Derived Technologies," "Sterilized Tools," and a few miscellaneous storage rooms. 

"My my, it seems DEM has developed quite a few interesting toys on this island," Kurumi's voice rang out from the darkness.

"Once we've secured [Sister], you're welcome to come back and take a look." Kyo sighed. "Let's continue onwards for now."

"You seem awfully preoccupied with [Sister]'s condition," Kurumi pointed out. "Could it be that you have some connection to her?"

"You know just as well as I what a terrifying strategic weapon she is." 

"That's not what I meant~" Kyo ignored Kurumi's probing as he walked towards a door labeled "Security Office/Records." Quickly throwing open the door, Kyo bashed in the head of the lone guard playing Minesweeper with the sheath of [Origin]. 

Only one person? Kyo quickly swept his gaze across the room. Aside for a lone desk and chair, an assortment of monitors, and a poster of what appeared to be a bunny, chicken, and bear, Kyo could see nothing but rows upon rows of labeled cabinets. Surely the security here isn't this lax. I can't shake the feeling that-

"What a violent display, Kyo. It's quite unbecoming of a gentleman." Kurumi observed from behind him. At some point she had manifested, her right eye shing with red light as she stared at him with intense scrutiny.

Kyo shook his head. "No one working on this island is an innocent, Kurumi. Not to us Spirits." Rummaging through a cabinet labeled "Human Trials", he picked out a folder, gave it a brief once-over, and tossed it to Kurumi with a shake of his head. "In fact, it seems they aren't exactly saints to humans either."

As Kurumi read over the document, her expression shifted from scrutinizing to concern to finally disgust. Throwing it into her shadow, she smiled mockingly. "So this is what the 'good guys' have been working on? Oh, how ironic."

Kyo ignored her. "Since we've taken care of the security guard, we're probably in the clear. Let's speedrun the rest of this mission. I'm starting to feel a weird chill."

—————I am the dividing line that shifts time and perspective—————

This Spirit is proving himself more and more interesting, Kurumi found herself thinking. The self-proclaimed time traveler had gone completely quiet since they had left the dead man in the security office. Kurumi had seen her fair share of death. As her title suggested, she was a [Nightmare] that reaped lives by her own sense of justice. However, she still never expected Kyo to suddenly showcase the same ruthlessness. He's more dangerous than I thought. 

"We're here." Kyo stopped at a door labeled "Live Experimental Testing Lab." Without hesitation, he slammed open the door and unsheathed his blade. Kurumi could hardly react before her vision was adorned with crimson splatters. 

"You..." Could I have reacted to that attack? There were at least twenty people in there just moments ago. Just what exactly is his Angel?

BEEEEEEEEEP- BEEEEEEEEEP- BEEEEEEEEEP-

And that would be the alarm he put so much effort into not triggering earlier.

Stepping over the fallen bodies, Kurumi was finally able to get a decent look of the lab. Dozens of isolated rooms lined the walls, each one containing some sort of monstrous humanoid. No, those aren't just humanoids. Those are-

"Those are the result of human experiments." Kyo interrupted as he walked out of another room. "Kurumi, I'm changing the plan. We're going with Scorched Earth."

"How heartless of you. I would have thought you would have at least tried to save these innocents?" Kurumi laughed uneasily. What's with this change in personality?

"There's no point. I vaguely noticed something strange earlier, but it's entirely clear to me now. These people-" Kyo pointed at the humanoids in the rooms, "have no hope left. I can feel it. The very air itself is thick with the despair of hundreds upon hundreds of those who live and once lived only for the release of death. Even if we saved them, their minds are unrecoverable." He pointed back at the room he had emerged from, then looked at Kurumi with eerily vacant eyes. "You can feel [Sister] just up ahead, right? I'll give you three minutes to evacuate her. When that time is up-

I will erase all the pain from this island, like tears disappearing in the rain."

——————I am the dividing line that shifts perspective——————

Three minutes left.

Kyo no longer felt cold. The peculiar coldness from before had long since been lost to a stifling emptiness that seemed to slow down and amplify the world around him. He could hear the memory of the wails and screams of humans that once lived. The dying heartbeats of the abominations behind the glass. He saw their final destination in the depths of the Nihility. He vaguely heard Kurumi call that [Sister] was secure. He could feel parts of [Sister]'s memory too. It brought an unfathomable hollowness to him.

Two minutes left.

Kyo could feel something off. The hilt of [Origin] shook as if warning him of an incoming disaster. However, had already chosen to sever the lingering pains of those who suffered on this island, and he would follow through. A part of him thought it was irrational, but he ignored that part. This would serve as both his personal justice and a warning to Westcott.

One minute left.

Focusing the power of Nihility into his blade, [Origin] began crackling with crimson lightning. [Naught] soon revealed itself, gleaming in its signature blood-red. Kyo's hair began to turn white as his hands were stained with red etchings of lightning. 

Ten seconds left.

Kyo was sure of it now. Something was off, terribly off. Acheron's warning of being tainted by the Nihility briefly crossed Kyo's mind before he narrowed his eyes and steeled himself. It was a meaningless warning. He would be fine.

Now.

Kyo's vision of reality overlapped with the Horizon of Existence. Roaring dark waves of black water had broken through the border between light and dark, tainting the pure white void that once coexisted with the stained black one.

Slowly unsheathing his sword, he began to speak to himself.

"I wish to mourn the departed, weeping endless tears, to carry their wordless cries beyond the horizon, leading them back home."

...

...

...

On March 31st in the year of 20XX, multiple agencies around the world detected a catastrophically large amount of energy released in the South Pacific Ocean. On that day, at approximately 14:44, every trace of Neryl Island ceased to exist.