Tsukino Moon, the sworn protector of Minato City, had to fight to suppress a yawn as she walked through streets and alleys in search of the monster that had been devouring innocent civilians. She would always remember the lessons that had been drilled into her as a naive young magical girl, of course. She was the defender of everything light and good, and the enemy of everything dark and sinister. Evil lurked in every shadow, and it was her duty to remain ever-vigilant against all its perils. But, after all these years, that didn't make her patrols any less boring. She had fought world-ending threat after world-ending threat, and she was still standing. One more little monster wasn't much to worry about.
Still, it was hurting people, and that meant it had to be stopped. According to the reports she'd heard, the monster manifested as some kind of strange, malevolent doppelganger that preyed on those who crossed its path. Tsukino wasn't sure where to look for it, so she was just patrolling the streets and waiting for it to strike.
Or, perhaps, stumbling across its lair.
Rounding a corner, Tsukino found herself facing a small alleyway that should not have been. It was darker than dark, and the deeper the magical girl peered, the more it seemed to collapse into something almost organic. The walls of the adjacent buildings became like solid shadow, illuminated only by odd, jagged crystals that reflected the night sky above into infinite shards of light.
Creepy. But not, Tsukino decided, the creepiest she'd seen. She wasn't afraid. Stepping forwards, the magical girl raised her enchanted scepter and smiled as it glowed with a warm, familiar light, keeping the unnatural dark at bay. Over the years, she had learned to work her magical sailor outfit into a slightly more tasteful lolita dress, something more appropriate for the physique she had grown into: toned, tough, and a little scarred. She kept the scepter the same, though, tacky as it was, with its big, pink, heart-shaped crystal. It was a nice reminder of things past.
She kept her old hairstyle, too. Twin, blonde buns on top of her head, and long, flowing pigtails behind. It was a signature look.
The deeper Tsukino went into the shadows, the darker and more encompassing they grew. She was no longer in an alley, but an expansive cave. The sky above her was gone, as were all the lights of the city, but the cave remained dimly illuminated by the crystals that jutted from every surface. Tsukino was no longer sure it was the night sky that they reflected. They seemed to glow like they were filled with stars, but were tinted with a sinister, purple hue.
Perhaps this strange place - this pocket dimension - was like a spider's web, Tsukino mused. She could easily imagine that civilians would find themselves hopelessly lost in the darkness, and become easy prey for the doppelgangers lurking within. Not her, though. She was far too strong for that.
"Oh? What do we have here? How interesting..."
Tsukino stiffened at the voice. It was uncomfortably familiar but it distorted slightly as it echoed throughout the strange, dark cave, and Tsukino couldn't quite place it. She knew, though, that nothing good would sound so at-easy in a place like this.
"Stop!" she called out. "In the name of the light, show yourself!"
The only answer she received to her command was a resounding and mirthful laugh. "Oh? It's you? That certainly is amusing."
"Show yo-"
Tsukino's lips froze when the other presence stepped closer, into the dim light. She recognized them at once, of course.
It was her.
Not really, of course. It couldn't have been. It was a cheap, poor, mocking imitation, but the resemblance was still striking enough to give Tsukino a moment's pause. The doppelganger, along with all its clothes, seemed to made of the same shadowy substance as the rest of the cave; it was all night sky and shimmering purple. As unnatural as it looked, though, it was clearly meant to be Tsukino. The silhouette was unmistakable, and there was a telltale familiarity in how it moved and carried itself. Those similarities were all the more repugnant, given the equally marked differences between the doppelganger and Tsukino.
The doppelganger carried no weapon, but it was wearing what Tsukino could only think of as a whorish parody of her own magical girl outfit. It had the same ribbons, the same folds and the same patterns, but it seemed to have been ripped to shreds in a way that had to be deliberately suggestive. The top barely covered her breasts, and the skirt had been cut so short it barely deserved to be called one. Everywhere, the outfit was raked with tears that allowed alluring flashes of soft, purple, corrupted skin to show through. The only part of the outfit that had been added to were the boots, which had metamorphosed into tall, impractical, fuck-me heels. This shadowy clone of Tsukino looked like something between a succubus and a streetwalker.
And the most unnerving thing of all was the too-wide grin, stretched across her otherwise featureless face.
Tsukino sniffed. She wasn't impressed. "What are you, some kind of shape-shifter? Stealing people's faces as you attack the innocent? If you expect this embarrassing display to unnerve me, you're sorely mistaken. In the name of the light, I will punish you!"
As she spoke, Tsukino made a familiar with her hands. As she did, the doppelganger, which had been slowly sashaying towards her, bent double in laughter.
"Oh my god! That's how it looks? And those words... ah, the naivety is thrilling! It's been so long."
Tsukino scowled. She was in no mood to let a demon mock her. "Are those your last words, fiend?"
The doppelganger's laughter died. "Last words? I hope not! Maybe instead I can correct a few of your misconceptions, hm? I'm not a shapeshifter. And I haven't attacked anybody."
"Ridiculous!" Tsukino pronounced. "I won't be fooled by your lies."
To her surprise, the doppelganger visibly cringed. "Ugh. So stuffy! I had forgotten how bad it was... well, tried to forget, anyway." She laughed. "Tell me, do you actually think I'm dangerous?"
That sounded like a trick question if Tsukino had ever heard one, but she had to admit that she sensed nothing from the shadowy being in front of her. No power, no hidden weapon. Nothing. "You're a monster."
"Didn't think so," the doppelganger tittered. "Next question: what do you think this place is?" She gestured at the cage around them.
"Some kind of pocket dimension you created," Tsukino growled. She was tired of being spoken to like this. "A way for you to lure and trap your victims."
"You're so dead set on being wrong," her doppelganger replied. "And I'm getting tired of explaining, so I'll just tell you. You've got it backwards. I didn't create this place. It created me. Or summoned me, I should say. This cave, it's like... a bubble of evil in the world. A bubble that went 'pop', leaving a scar on the face of reality. A rupture."
"And it... what?" Despite herself, Tsukino wanted to understand. "Copies people?"
"Closer!" the doppelganger said approvingly. "But I said it summoned me, remember? I believe this cave is a rupture between realities. It manifests an alternative version of anyone who encounters it. The worst version, from across every timeline it can reach, made real and solid in living shadow. That's why people keep getting attacked, I'm sure. Probably, the worst possible version of your average Joe is some kind of crazy, violet psycho." She laughed mirthlessly. "We've been seen how far people can unravel under the right strain, I bet."
"Then you're..."
Tsukino had to remind herself to keep her guard up as she was drawn in by the doppelganger's explanation. This, this being, was the worst possible version of her? She could scarcely imagine what that might mean, but she knew it had to be bad news. In all her years fighting against evil, all manner of beings had tried to corrupt her and lure her to their side. Which of them was the worst? Queen Detaria? The Black Star Clan? Lady Galaxia? Tsukino dreaded to imagine the kind of dark powers promised to a version of herself that had succumbed to their evil. The divine powers of a magical girl, married to the boundless darkness of those devils? The strange thing was, though, that this doppelganger - this Shadow Tsukino - didn't seem powerful at all. She seemed disheveled and undignified. She had no weapon. She seemed weak. What did that mean?
Tsukino straightened her back and held up her scepter. It didn't matter. All that mattered was her duty.
"Listen to me, fiend!" she cried, in the voice that had given hope to the hearts of thousands. "I don't care what you are. I don't care of you really are an alternate version of me. It won't matter. I don't care what dark bargains you made, or what corruptive powers you drew upon. It won't be enough to triumph over my goodness, kindness and love! In the name of the light, I vow to cast you down!"
Shadow Tsukino was just a few paces away from her now, but as Tsukino made her vow, the doppelganger threw back her head and laughed an odd, shrill laugh. "Oh, you just don't get it, do you? You can't even imagine what I really am."
"I told you," Tsukino insisted. "It won't matter what kind of evil deal you made, or who you made it w-"
Shadow Tsukino's laugh just rose in volume, cutting her off. "You don't get it," she retorted. "You don't see. My other self, I'm not the version of you that fell. No, not at all. I know all the temptations you've faced and resisted, but I'm here to tell you that there's something worse than all of that."
"What?" Tsukino was tired of all this grandstanding.
