I pulled this off the shelf at random to watch again. It’s a 12-episode TV series from 2003, later made available in the US by Geneon, and there is also a related movie (or OVA) series “Kara no Kyoukai” from 2007.
While some old series turn out not to have stood the test of time, this series seems even better on second viewing than I remembered. The orphaned Shiki returns to live with what remains of his family, but finds that unpleasant and frightening events are happening around him.   Shiki is not quite what he seems, or even who we thought he was, and the same applies to several other characters, that is, they’re not quite human.
In particular Shiki becomes involved with the white vampire Arcued, who insists that Shiki killed her and chopped her into 17 pieces. Indeed Shiki has a strange ability to see “lines” and when he cuts along these lines with his knife, things fall apart.
Shiki is put under severe stress. His schoolmates note a change in him, but obviously he can’t tell them the truth. He is terrified by the situations Arcueid leads him into, and in his new home he has to resort to sneaking out at night to meet Arcueid and evade the watchful eyes of his beautiful but severe sister, Akiha. The growing relationship between Arcueid and Shiki is well-handled, and the dialog, delivered by some fine voice-actors , makes this unlikely relationship the more believable. For once, it’s played as a straight drama, with little or no attempt to over-egg it or inject humour.
The least succesful characters are the ordinary school students, who appear sketchily defined and irritating.