Disclaimer: If I own Kuroshitsuji, Sebastian would have at least showed some kind of expression when he was told to have became the demon Ceil's eternal butler at the end of season II.

AZA'ZEL

-Hebrew word, meaning "entire removal" and "scapegoat."

Chapter One – Not a Mistake

Sebastian was fairly young by demon standards when he encountered Ciel. And let's just say, all the worst mistakes are most likely to be made in the teenage years, human and demon alike, and the worst? You cannot even bring yourself to admit to anyone it was a mistake.

Sebastian was unique in his own right, his talents great for one of his "age", and sadly, his mistakes tend to share the same characteristic

Years later, he thought of that famous quote, "what was once lost, will be lost forever."

"Not necessarily," he smirked, he was not just any of those filthy Lucifer's recruit from the kicked-outs of heaven's gate, he was a demon by choice and harbored the power from his ex-occupation.

He would see his young master again.

It was not a human crafted flask, to carry such a trinket would be degrading, for both him and the soul within. Instead, he chose a natural piece of crystal, hollowed out by liquid razors after thousands of years, with a token of remembrance serving both as the stopper and the label.

It was a small crystal bottle barely larger than the sized of his human palm, of a deep midnight blue hue with a familiar sapphire ring encased in its red crystal stopper.

He was probably the first ever to bottle a soul.

For the hundred or so years after the end, he feasted on souls almost uncontrollably. Day in, day out, he slaughtered and fed and still felt so incredibly empty. He swore to himself that he would not make another contract again… such things take so much out of a demon…or is it just him?

Someday, he'd just find a seclude spot in hell's forest, and caress he flask he carries and lose himself in its scent.

He did not drink. When the flask drains empty, he'd have to answer the next question: "now what?" He did not know the answer. And that is simply unacceptable.

He idly strode in and out the hell-fire, inspecting various scenes of fallen human's eternal suffering. And he thinks, if he had not appeared before him on that fateful day, would he be here now? Then he thought perhaps that's not a bad proposition at all, he fingers the hidden jewel of blue crystal, and allowed himself a moment to entertain such thoughts.

When another summons resonated across hell like those of a fire-alarm in modern human world, he did not look up. It was one of the many, soon, some demons bored out their mind would fly to answer it. It has nothing to do with him, after all, he had long sworn not to….

Teenage promises were made to be broken.

As if in a deija vu, he heard the sneakers raising up left and right, "Ha, a child!" "How weak," "Barely a mouthful!" And he raises his head so fast that a whirl of feathers fell, and for a tiny fraction of a second, he stared at the dark haired boy in bewilderment, and calls out…

Only to see he was already died. A child almost never survives the ceremony.

He began to make contracts again. Working did seem to improve the quality of one's meal, though not by much.

His peers (not equals, never equals!) smirks with spite when he passed, "What's up with you and kids?"

Then he suddenly realizes all his contractors after him had been 13 or younger. And so far, none survived to 14 years old.

He's tired of seeing not what he expected. Every word, every order, ever gesture, ever command…he's tired of seeing not what he wanted to see.

Wait, what did he want to see?

He had long ago ceased to carry the precious crystal with him. He could not enter a contract holding something to lose. When he returned after the meager meal of a typical orphan, he found the ground which he buried the treasure under thriving with a flood of sterling silver roses which definitely was a first in the realms of hell.

He wished to see him again, flesh and blood, not just silvery mist confined within the crystal palace, with a sapphire ring as its seal.

So he would.

The demon grudgingly admitted over time, that he might have made a rather inconvenient decision, at one time, but not a mistake, never a mistake.

To be continued…