Fridge Horror: Various characters mention that priests are losing their powers with each successive generation. And the fact that Kurumi won't be able to bear Nakahito's children, as well as being a Clingy Jealous Girl (he probably never or couldn't get married because of this, so Nako is probably descended from Nakahito's brother) means she's just speeding this process up. And Mk. II Kurumi can't have kids with Nako either. That's not to say there can't be more priests with strong powers such as Nakahito and Nako, but she's certainly not helping things.
Ho Yay - Between Nakahito and Mikhail (particularly in the manga, where Mikhail doesn't have a female form).