Demons had free will, too. To a certain extent, of course. Just as angels had free will.
But the love he harbored was anything but free. When he first felt the stirrings, he thought that the boy had somehow forced him to love him. Later on, as his master showed no signs of reciprocating his hidden love, he realized he had been trapped, and not by Ciel. He had trapped himself. He was chained, and he liked it. He had a burning desire. Though he had not a heart, he ached for his master with all his being, all he was.
Ciel bid him to lay next to him for a single night. With wet eyes, he asked for him to embrace him until morning. He looked so small, clasped in his arms. Ciel sniffled, and shivered against the cold body that was anything but inside. The hot tears splashed ceaselessly against the impeccable suit, only seen by Sebastian's eyes. They eventually stopped, and he pressed the tiny form closer, and caressed his forehead lovingly. In this moment, only the two of them existed. The demon decided to sleep, although he had no need to.
As the next morning came, the butler was left with only his thoughts and empty sheets. When he reached the dining room, he was met with a frown.
"You're late." The tone was hard, but his eyes had softened from before. "Sebastian, get to work. I'll pardon you for now."
"Yes, my lord." He walked into the kitchen. Bitterness filled his mouth. At times, he wondered who really was heartless between the both of them. Everything had returned to normal, the semblances of the night before torn to shreds by the daylight.