AN: Takes place during Tsukuyomi and Setsuna's final battle.
Out of all the many things she's killed, all the many opponents she's faced, Tsukuyomi thinks that humans suit her best. She has the very slight impression that they might disagree, but what they want is hardly the point.
Tsukuyomi skewers Setsuna's hand on the rock.
There is a charm to them that even her considerable talent can't seem to destroy. At the ends of their lives, they look into her eyes with such honest, straightforward hate and confusion and anguish. They don't limit themselves; they simply feel and she gets to watch as her swords (hers!) plunge in and drain them of every last drop.
After a long day of dueling nothing but stoic demons and other higher beings, it can be very refreshing.
Setsuna's artifact flies at her head.
That's how humans should be. That's how everything should be. Dancing across the lines of life and death with a silent partner means nothing at all. Outrage, bloodlust, and a hungry want for life should erupt constantly on the battlefield so that the thrill and promise of death always seems near.
Demons have never given her that. Dolls are incapable of it.
But humans. Humans and their open expressions delight her. There is life to be taken in them, even if it is weaker than many other creatures'.
Tsukuyomi catches the knife and drives it into Setsuna's shoulder.
Even outside her chosen battlefields, that honesty has its appeal. On days when her contracts demand discretion, looking into someone's eyes, seeing all they hold dear, and imagining ripping it away in gory bliss is usually almost enough to keep her satisfied.
That, she thinks, was the only part of Setsuna that was fascinating. The way her eyes flared whenever the Konoe girl was threatened sent shivers down her spine—but everything else about the bodyguard was so stoic and dull. Her demon half must have sucked all of her human spirit away. Her straightforward devotion was the only interesting thing.
Setsuna collapses against the rocks.
And then Setsuna introduced her to the incandescent pleasure that dishonesty allows.
It was the quietest of lies, muttered to no one in the middle of a wild, magical forest.
"I'm not worried."
After a day of watching the half-demon tear through the wilderness in search of that girl (who made Senpai's eyes shine just so), Tsukuyomi barely managed to put up a silence ward before laughter came tumbling out of her.
And that—that wasn't even the best part! She can remember that look that came over her Senpai's face when she said that—she believed herself! Somehow, someway, Setsuna had tricked herself into believing that silly little lie—and—and—
Tsukuyomi tenderly licks the blood away from her eye.
It makes Tsukuyomi want to start laughing all over again, because that's the moment it really started. Fate is an interesting boss, and gave her tasks that kept her mildly entertained. That was usually good enough, and she would have—well, maybe not happily, exactly, but she wouldn't have complained much if her assignment went precisely as planned.
But then there was Setsuna.
A duller shade of red spreads on Setsuna's cheeks.
Setsuna, and that one moment of pure glee.
Tsukuyomi presses her head against Setsuna's and laughs.
Half-demons had never really concerned Tsukuyomi before. The ones raised by their demon parents acted like demons. Or died. Both, for the ones she met officially. The ones raised by their human parents—
—Well, truthfully, she's never met one like that before.
She has to think that Setsuna is some twisted, delightful combination of the two, though. A demon raised by the sword who acts like a human.
A demon who wants to be a human.
"I have to ask, Senpai. Wherever have your wings gone?"
Tsukuyomi has to wonder what it was that made Setsuna start wanting things for herself. The soldier from Kyoto had only one desire, and would have happily endured any misery to see it fulfilled. Appealing, but so, so shallow. A blank slate to be sacrificed. Only good for a temporary thrill whenever her eyes burned with righteous indignation.
But then the soldier began to fade, and a demonic human started to take her place.
She thinks, for an awful moment, that Setsuna won't answer.
Setsuna started wanting.
She wanted peace. She resented the fights that forced her to take to the skies. She wanted all of her friends to make it home safe and sound; she wanted to go back to a life that didn't involve daily fighting and fretting over her personal princess.
And more than anything, she wanted herself to believe that.
Then Setsuna looks away, more embarrassment written in her eyes, and slams their heads together.
It's incredibly endearing. Out of all the blunt honesty Tsukuyomi ever played witness to, the frantic desperation that Setsuna still throws into her feigned humanity is the most delectable. Even if she cared to resist, she doubts she could help being entranced.
Tsukuyomi sees stars.
She wants to be the one to destroy her Senpai's precious illusion. She wants those careful walls of what is proper for good little humans to think broken beyond repair, and she wants Setsuna to—
And then she gets her answer. "You said…"
She wants Setsuna.
She thought she understood restraint before this. It was an annoying but necessary part of her employment. People only wanted the bodies to show up at certain times. She would hold off from attacking because of that requirement.
But then Setsuna happened.
"You said that as long as I'm human, I can't beat you."
And now she knows what restraint does. She's felt the rabid desire that comes from being deprived of the one thing in the world that she wants above all else. She knows the rush of euphoria that bursts in triumph when she finally, finally gets to have her prize and there's no one to say that she can't let the anguish and lust and fire loose and do whatever she pleases.
Setsuna doesn't say that Tsukuyomi was right.
Her dear Senpai has no understanding of such glorious concepts.
Tsukuyomi smiles indulgently.
But she will. She'll know exactly how all of that feels when her lies fall to pieces around her and she gets a taste of those hidden truths she's not supposed to think about.
Tsukuyomi will be the one to enlighten her.
"Senpai," she breathes, "you were never human to begin with."