Source for this is
this Cave blog post. It mentions a Death Smiles drama CD as well, so I'm guessing there's a volume 2 coming out.
The page doesn't specifically credit 山岸由香 (I'm guessing Yuka Yamagishi;
this looks like her blog) with vocals, but most hits on the name mention vocals and she's worked with Yasuhiko Fukuda before with him doing arrangement and her doing vocals.
Here's something about an event they did.