The shows follows Saya Otonashi who is high school girl with amnesia living in Okinawa. However, he peacful life is shattered when she discovers that she is in fact one of the last living vampire's and her blood is the only weapon against strange vampire like monsters called Chiropterans. As such she sets off to defeat them once and for all.
This is a great show. It has some great fight sequences and some really interesting characters. In particular the relationship of Saya with her adoptive family - especially in later epsiodes when her memory returns is really compelling. The supporting cast are very well written and in my opinion one of the strongest elements of the show.
This is a really brilliant show which more people should be watching.