A doujin (self-published) work released at Comiket, Tsukihime is a visual novel about Tohno Shiki, a teenage boy who's had the mysterious ability to see the "lines" of death all things have - that if cut, will spell their end - after a car-crash during his youth.
Cast out from his birth family, the Tohno, due to poor health, after 8 years, Shiki returns to his home once his father dies to find that things have changed. His timid sister Akiha has become the headstrong young head of the family in his absence, and the young girl(s) he remembers from his youth have since become the family help as maids. Living in his old childhood home, Shiki is swept into a world almost completely alien to him - for reasons that have nothing to do with his home.
One day, Shiki finds a beautiful woman, and kills her for seemingly no reason.
The following day, he sees her waiting for him on his way to school.
She, Arcueid Brunestud, is a vampire. One on the hunt for another of kind, that has taken up base in Shiki's town. Considering how him killing has set her back quite a bit and heavily weakened her, she's dead set of making him take responsibility for killing her.
And so Shiki finds himself drawn into the world of the Vampires known as the Dead Apostles...
At least, during the Near Side of the Moon...