I'm beginning to think the Viscount Druitt might actually be important.
Just recall how many dangerous situations he’s escaped from, almost without explanation.
Honestly. The man has appeared in most of the plot arcs (4/7 by my count). I believe the Noah’s Ark Circus, Ciel’s House Murder and the German Witch (to the point it’s at now) are the only ones he’s been completely left out of. Out of the ones he was in, he played major roles in two: Jack the Ripper and the Bizarre Dolls.
It makes me consider that he might not just keep reappearing for comedic relief. He might actually end up being important to the plotline.
After all, it would be true literary parallelism, wouldn’t it? For the Viscount to be Ciel’s first and last case. (That we see, of course.)