Author's Note: I doubt anyone will even like this, but it's been awhile since I've written anything actually dark. May have gone too far on the spectrum but hey, go big or go home, right?

Don't know if I'll continue this or not, but it's currently set before the main storyline, and with Rin being a girl so I guess it has multi-chapter potential.

Disclaimer: I don't own anything.

Obsession

ob - ses - sion (uh b-sesh-uh n)

noun

1. the domination of one's thoughts or feelings by a persistent idea, image, desire ect.

2. the idea, image, desire, feeling ect. itself

3. a persistent idea or impulse that continually forces its way into consciousness, often associated with anxiety and mental illness

4. the act of obsessing, or the state of being obsessed

For some reason when he saw her the definition popped up unbidden in his mind.

Even just the simple glance through his streaked glasses was enough to send his thoughts into utter disarray.

His intellectually driven mind immediately tried to categorize the tug of emotion in his gut.

Respect?

No. Though that wasn't to say he didn't have any for her.

Love?

No. Well of course he loved his sister, though this felt oddly different.

Admiration?

No. He admired many things about her, but not in a way that would evoke such a feeling.

Obsession?

Plausible.

He scrambled to come up with some explanation for the connection.

She and that word - obsession - shouldn't fit together so perfectly.

As if on cue, stilled images of her shuffled through his mind.

A picture of her grinning at something he said. No hidden emotion or patronizing mirth - just pure, unadulterated happiness.

A snapshot of her wiping away tears, trying to put on a strong front for him.

How much he had wanted to hold her then.

There were a lot of things he wanted to do, but couldn't - like now for example.

Inhaling and exhaling slowly, he watched the rise and fall of her chest, his own breathing syncing up with her sleeping rhythm.

His next breath however hitched, as her beauty stole yet another from his unwilling lips.

The moonlight streaming in through the window caught her pale skin at the perfect angle - giving her an ethereal glow in the near darkness.

Through the sheets he could also make out the outline of her covered body, which he didn't need to see directly to know. He had it committed to memory after all. The curve of her back. The waving of her newly developed curves. Even down to every freckle. He memorized it all.

Her raven hair, which was sprawled out around her pillow like a halo of darkness, caught his attention yet again. For some reason it was his favorite part about her.

As if on its own volition a hand reached toward a black tendril, but he caught himself just before it could grip even a single, silky strand.

What was he doing?

Now that, his genius brain had no answer for.

Careful not to wake her, he stepped lightly away from the edge of her bed, the floorboards creaking under his weight though not loud enough to stir her.

Taking the chair from his desk like he did every night, he delicately carried it back to his sister's room, where he perched it at the foot of her bed.

Not taking his eyes off her, he slid into the chair, resting his chin on top of his steepled fingers.

Then, as he had many nights before, he sat there, watching over his sister until dawn.

Soon, he would no longer be able to do this though.

As much as he craved - needed - to do this, it wasn't right.

Though it wasn't the whole reason, he couldn't say distancing himself from her wasn't a factor in why he wanted to go away for school.

Sure, the idea of separation was, well, too debilitating to even imagine, he knew it was the right thing to do. He wasn't quite sure what these obsessive feelings were, but there was no way she would ever return them. Not that he even wanted her to.

A part of him just needed to accept that this wasn't normal - that he wasn't normal.

As he got up to leave, he sent her one last fleeting look.

Rin - his sister - his fixation - his obsession.

Soon he would say his goodbye, and she would never have to know what her brother truly was: obsessed.