This is not the genre of show I will keep watching, but I thought the first episode was pretty good. I liked being thrown into the action and forced to figure things out as I went along. I liked the character design. The monsters were as well done as monsters can be (I don't do monsters).
And I liked the voice acting. I thought both
Chihara Minori and the newcomer,
Takagaki Ayahi, were good. I also liked
Tsuji Ayumi (who plays Rose in Red Garden) as Lola, the apparent servant girl. The first victim,
Mochizuki Hisao, a well-known second-tier
seiyuu who played little Princess Valkyrie, was also pretty striking.
By the way, I double-checked the on-screen credits, and it's Minorin playing Sumire so well and the newcomer playing Lucia (also quite well).