While I might amend my opinion on calling him asexual, after people have pointed out various things, the fact is that he is extremely picky about his potential romantic interest. He has made that abundantly clear. Not picky in the stupid sense of fantasy high expectations of "needs to be a blonde with blue eyes, big boobs, good sense of humour, wise in using money, intelligent, can sing and play instruments, not overly jealous or controlling, etc", but picky in the sense that there's only one in a million women that does trigger anything in him, for unspecified reasons.