A/N: This was actually inspired by chapter 20, where it really became apparent. I've mentioned before that I love the kind of complex relationship shared by Sebastian and Ciel, and I wanted to bring out another aspect of it. Ciel and Sebastian always seem to be trying to get the other to show weakness. Since Sebastian possesses no human error, Ciel seems to always be trying to make his butler slip, putting him in uncomfortable situations to see how he would react (cough currylol). But here, Sebastian's only weakness is simply that he possesses no human error. That is his error. Enough rant, enjoy!

All characters of Kuroshitsuji © Toboso Yana

Human Error

"This," Ciel Phantomhive sighed, taking his hand away from the fingerboard, "is why I hate contemporary music."

"Come now, Bocchan. It's a good learning experience," The Phantomhive's pedagogic butler, Sebastian Michaelis replied. He reached out with a white glove, taking the boy's hand and placing it back on the small strip of ebony. Ciel did not resume his playing, and merely fixed his butler with an incredulous stare.

"A good learning experience? There is no way I can learn the Scottish Fantasy, Sebastian!"

Sebastian's expression remained immutable, save for a slight arch of the eyebrows. "Are you saying that you lack the skill to play Bruch's latest composition?" he inquired.

Ciel made a little 'tch' sound through his teeth and lowered his Guaneri violin, bow tip grazing the carpet.

"I'm just saying that the techniques in this piece would take hours of practice to master. It is on a different level than a Bach Chaconne," Ciel inveighed, trying to conceal his irritability. Most ventures came easily to the precocious Phantomhive, and any aberration from that routine was regarded with the utmost annoyance.

Sebastian gazed at the score for a moment, deep ruby irises washing over the notes. "I do not think it is so difficult," he remarked thoughtfully, before holding out an elegant arm. "Allow me to demonstrate then, Bocchan."

Ciel glowered but handed over his violin and bow to the butler, who, after removing his gloves, began to play. Immediately the room was rife with the mellifluous harmonies of Bruch. Sebastian's techniques were flawless, the vibrato rich and wide; the bow changes smooth and without unnecessary swells. The slow parts sang with the ringing melancholy of graveyard bells, and the fast, high sections fully demonstrated his musical prowess.

When he was finished, Sebastian returned the instrument to the young master, his pale face tinctured with satisfaction. The chin-rest was cold, Ciel noted, as he held the violin on both ends.

"See?" Sebastian said, slipping his gloves back over his fingers. "It certainly is not impossible since I can play it perfectly, even sightreading. What kind of butler would I be, if I couldn't even do that?"

He looked over, anticipating the humored smile that generally plagued the young master's features when he would astound the humans with his abilities. The master's blue eye would usually be crinkled up with a conglomerate of amusement, awe, and possession; the ends of his lips would be slightly raised as well.

Ciel indeed wore a smile, however it was not the one that Sebastian had expected. His uncovered eye was lazily half-lidded, and his smile was colder than the December winds outside.

"You're wrong, Sebastian," the boy said quietly. "It wasn't perfect."

It had been a while since anything said by a human had caught Sebastian off-guard, but this certainly had. Rarely did he find himself uncomprehending of a voiced statement. He blinked once, snapping his glove into place and asked, "What did not satisfy you?"

The boy's smile widened the slightest fraction, so small that it was only noticeable by his butler. "Your technical skills, fingerings, and bowings were flawless, as expected of a Phantomhive butler," he began.

"But the musicality and passion that makes the piece alive…can only come from a human."

Sebastian was silent, regarding Ciel through the few rogue strands of black fringes that had fallen in front of his eyes. His silence urged the boy to continue.

"Your playing was certainly musical, Sebastian, and all of your phrases were in the right places," he began.

"Then what was wrong with it?" the butler asked.

"Your musicality was tenuous," replied Ciel, folding his arms knowingly. "Humans in this world, as you've observed, feel strong emotions that fluctuate as easily as a delicate flower in the wind. They project all of their angers, their sorrows, joys—their hearts into their playing."

"But," Sebastian smoothly interjected, "As a demon, I do not possess that kind of human error. I am without those feelings, those…weaknesses."

Ciel gave a slight shrug. "Then your playing will never be perfect," he said. "You'll never know what it's like to feel the music, and you'll always be playing just the notes on the page, Sebastian."

"Are you implying that human error makes music complete?"

Ciel walked over to his desk, placing his Guaneri back into its velvet case. "A peculiar way of putting it, but I might be."

Sebastian let a twisted grin worm its way onto his face. "Then Bocchan will be the finest violinist yet," he proclaimed in a tone of sly ambiguity.

Taking no note of the comment, Ciel merely smiled to himself, victorious, for he had won the battle today.