To vampires, rape is a form of love making.Thus, their rapes and attempted rapes aren't so much evil as they are a manifestation of Blue-and-Orange Morality.
Tachibana can reproduceHybrid or not she did get a dose of Karins magic blood, and reacted to it
When Sophia was freed so was the vampires dependanceWhile Sophia was the key to vampire fertility she was also what stunted it. But now that she's free so are the vampires.
When Usei Kanon grows up she'll become a fertility doctorSeems like a good career for the former goddess of vampire fertility.