Firstly, woops! I scanned at 300 dpi instead of the usual 150. As such, this image is very large.

Second, yes, a yokai, specifically an oni girl. She enjoys playing with her slave, a commoner boy, to whom she also gave the ability to transform into a dog. She can be evil and somewhat of a glutton, but she's hemophobic (fear of blood) and thinks humans taste terrible (cough medicine), so she's not a terribly destructive oni. She mostly enjoys staying at home, drinking bowls of tea and various soups while her slave does random chores.

As for the picture, I think he's expecting some gratitude or a reward, which she's entertaining the thought of. I don't really know, it just seemed cute and a little odd, which is how I like my cute. (though strait up cute will do)