This is the character Mito Mashiro, the main heroine from the visual novel/eroge [Tayutama: Kiss on my Deity](http://en.wikipedia.org/wiki/Tayutama:_Kiss_on_my_Deity) by studio Lump of Sugar. It has a 2009 anime adaptation, but I think the image posted is taken from the VN directly. She is the incarnation of a goddess, and her goal is to bring harmony between humans and a fictional supernatural race called Tayutai. She also falls in love with the protagonist.

Here's a similar picture from the visual novel. It's a slightly different pose, but I think it's clear that it's still her.

![Mito Mashiro][1]

  [1]: http://i.stack.imgur.com/UUzOf.png