Responses
They're a pair now, en already took ichii's blood way before so the only thing they needed to do is for ichii to take en's blood. in vol 4 it will probably be more about the lore and the origins of fangs but I think I remember reading a post from the author's Twitter that en and ichii will also still appear in vol 4 for their relationship to actually grow more

Did En finally become Ichii's pair? Because I saw Ichii bite him, but didn't see En doing the same.
Also, is volume 4 going to be about the 5 originals and their past? Orrrrrr