So, it seems that Subaru and Kamui have known Yuuko for some time now. They visited her to obtain the power to cross dimensions as well. I wonder what their price was. I think that the pendants are the means by which the two cross dimensions. I am curious what Kamui meant about that hunter becoming a hindrance. Why was Kamui so adamant about Subaru not giving his vitae again? Is it because each time they give their vitae, they weaken themselves? Or is it simply that Kamui did not Subaru to risk getting hurt if someone tried to tamper with his vitae? Yuuko said that the twins are purebred vampires. That seems to suggest that there are other vampires of lesser lineages, even half-breeds, who do not have such potent vitae and abilities as these two. I think it's charming really, the relationship between this Kamui and Subaru. They do seem to care greatly for each other. It's the love shared between family members, specifically siblings. Subaru is the same as his other self, before that Subaru was traumatized by that Seishirou. This Subaru also seems too kind for his own good. Therefore, it's fortunate he has a very protective brother this time. Kamui would probably take great pleasure in eviscerating anyone who dares to try harming his twin.
In a way, one could say that Fai has been sired by Kamui, so that makes him Kamui's childe. Since Subaru gave his blood to Seishirou, that would make Seishirou the childe of Subaru. In a way, Fai and Seishirou are cosanguineous, of the same bloodline. Even if he is only a half-breed, Fai will probably gain some heightened strength, speed, reflexes, regenerative capabilities, as well as growing those long claws at will, hopefully. Kurogane and Fai are linked to Kamui in a way now, since Kamui's vitae flows through the two. I wonder how this development will affect their interaction with Kamui, since he did save Fai's life just now, if only for Subaru's sake.