There's small question marks next to the tags of an image on the left - clicking on them will take you to the appropriate wiki entry for the tag (if one exits).
But to answer the question, it's Sakuya Izayoi from the Touhou series (as the tags tell), maid of lolivampire Remilia Scarlet, and whose hobbies include mainly knives,obessing over her mistress, stopping time, and stabbing the doorguard with said knives, not neccesarely in that order.
