[Looking back he'll likely think of it as a learning experience, at least to a degree. Understanding the way humans work... it's "more convenient" in the end, after all.]
Quite, young master. Desperation, as well. [Humans do so many foolish things out of desperation, too. So many desperate moments among those memories.]
[They're not as deep in as Ciel probably thinks. Deep enough not to run much risk of meeting anyone but still not at the very heart of the forest. Even Sebastian can't go there and not pay the monsters his full attention. Perhaps noticing something in Ciel's posture, or simply assuming they're heading back, Sebastian cants hid head vaguely to indicate their surroundings.]
The creatures here don't learn. [No matter how often he goes in here, no matter how many monsters he kills, they never learn to stay clear of him.] They will not stay away for long.
[Sure Sebastian can just slay them as they head back, but it will take time and... it might not be that fun to watch for Ciel. Carrying will be easier?]