Well it's not really confirmed that he loved her. The reason he could obviously never be with her (and honestly why would he want to) is because he hadn't planned on staying a human at all. He still really doesn't. When it comes down to it, he's a demon and that's all there is to it. Also I think they've both heard of each other but I don't think they had a past together specifically. I'll take the liberty of removing whoever put that.
Kurama: (response to Maya's love declaration) "I'm sorry." (thinking) It's too dangerous to tell you... how I really feel.