Here is a promotional video showing the three main female seiyuus from Ichiban Ushiro no Dai Maou talking about the show and their characters:
Toyosaki Aki (left) talks about her character, red-haired Soga Keena, being a magician who can make herself invisible, but has to take off all her clothes to do it. She calls her a "forest girl."
Yuuki Aoi (center) describes her character Korone, saying that she is an android with a little tail that is her on-off switch, and says that when the tail is pulled she makes a sound. The other two seiyuu laugh when she makes the sound, because she makes a very neutral sound quite unlike the sexy sound she makes in the anime, and which young Ao-chan apparently had a lot of trouble learning to make.
Hikasa Youko (right), who was Mio in K-On, says her character, Hattori Junko, is easily embarrassed, and speaks like a man.
These three also do the show's radio program together.