Part of a gift/trade with https://www.furaffinity.net/user/ivanks/ . During a magical ceremony, Rin Tohasaka is disturbed from her concentration by a series of loud and disconcerting noises from another room. She breaks off her project and investigates, coming face to face with two sets of red eyes in the darkness and a mass of black, bristling feathers on the floor. She turns to run, but her initial shock turns to curiosity and then desire, her former pursuits all but forgotten as she returns to give into her unleashed carnal urges...