She'd always enjoyed watching him; not in some silly, perverted sense like so many other girls would have, but just watching, as he trained or sparred or something, anything really. She'd been lucky enough to be one of the few he trusted enough to get close to, the only female he'd ever trusted, and she knew it too, knew that the trust went both ways and that she didn't exactly trust anyone else like she trusted him, either.
Trust had always run deep in their relationship, because it was what their friendship was essentially founded on. Not love or lust of a thirst for companionship, but trust. She'd lost her whole team when she'd barely been out of the Academy three months, lost her sensei and her brother and the only other non-familial male in her life, the one she'd always been told by her parents that she'd end up marrying for the good of the clan. She'd lost her foundation for trust, until the Third Hokage had made the long-awaited decision that moved her up to the ANBU Black Ops at the tender (or so her mother claimed) age of fifteen. She'd been put in his squad, under his tutelage, and granted he'd scoffed at the thought of having the first female ANBU member on his team, but they'd gotten used to each other after a while, spent more and more time in each other's company and finally realized that they'd both regained that elusive thing other people called 'trust'.
She'd been there when he stopped training halfway through the time he normally allotted himself and just clenched his fists so tightly that blood had dripped from his palms. He'd trusted her enough to tell her what the village elders had ordered him to do to his clan, trusted her enough to confess that he wouldn't be able to kill his otouto.
She, in turn, had trusted him enough to tell him that if he was going to be doing any killing, that he might as well start with her, since undoubtedly the village elders would never let her live now that she knew the truth, and she'd much rather die by his hand then by theirs. He'd gaped at her, then blatantly refused because she wasn't an Uchiha and what did it matter to the village elders, then. She'd just shook her head and walked over to him, then raised the hand he still clenched his kunai in and put it at her neck.
Sever the carotid vein where the jaw meets the neck; it might be messy, but it'll be relatively quick, maybe even painless. Besides, you're wearing all black; when the blood dries, no one'll even notice. Or you could break my neck, slit my throat, and let me bleed out on the ground.
Her eyes had begged him to, and so he had.
But not before he kissed her and offered a choked apology. She'd just smiled at him.
It's all right. I'll get to see sensei and aniki again, and teishu won't even be mad—not really. She'd paused. He was only thirteen, you know...
He'd nodded, and his hand twitched.
Later, when his little otouto ran after him screaming, and the frenzied yells of two or three medic-nin could be heard from the ANBU training grounds, he'd taken a scant moment to glance down at his black clothes and choke back a sound.
She'd been right. When the blood dried, no one could even notice...