[Anchor? For the last few years, has there been any anchor in Ciel's life but Sebastian? If Ciel doesn't grab on to him first, Sebastian reaches to hold Ciel's upper arms - pins him with such practiced methodicalness one might think this is a regular occurrence for him.
A vampire's victims do, after all, sometimes struggle.
The noises Ciel makes, the way his entire body convulses... it should be terrible to witness. Yet Sebastian only smiles, burning yellow eyes fixed on Ciel's face as if he wants to soak up every pained nuance of it. "Whatever happens, my blood will turn him. Nothing can stop that." Just a few minutes more, and then nothing and no one can ever again hope to steal this person from Sebastian. It's exhilarating.
It would perhaps be kinder to Ciel to ask Yona for some privacy, to let him be this vulnerable only in front of someone who knows him well, but Sebastian doesn't tell her to leave. Neither does he thank her, or ask her to stay - perhaps he simply doesn't care what she chooses to do from here on.]