Welp. New page was started.
@Ai no Miko: For Sebastian in particular, as Libis said, a sharper chin would help. Some more contouring around certain areas would help for more a masculine appearance. As for Kurama, again, a sharper chin would help, but it looks well done besides that. Other than that, I'd say you shouldn't have much difficulty in passing as a man.
Ok, let's try this again.
(Note: Left dates back to November 2011. Right is about a year after.)