[Sebastian reaches out to capture Ciel's chin, holding it in place with a gentle firmness. An affectionate, tender gesture or simply to prevent Ciel from moving around and aggravating his injuries?]
I am never to leave your side; you are never to leave mine, is that not right? Your death isn't allowed.
[Whether Sebastian means it as reassurance that he's going to prevent it, a demand that Ciel better not even think about giving in, or a firm belief that the very fabric of existence itself would collapse before allowing something so unthinkable to happen - is unclear. Perhaps he means all three at once.]