It's a question of biology... Vulcan biology. Towards the end of the 5 year mission, Kirk realizes that his feelings for Spock are requited, but Spock has already decided they can never be together. Kirk/Spock pre-slash to slash, with plenty of angst. (A full, clean copy for download - minus author notes, but including translations - is linked from the author's profile.)

Alucard and Integra are stranded on an island together, and Integra is Alucard's only source of sustenance.