I wanted to say this at a later date, but oh well. At the conclusion of the story, Yu and Yuki will return to Japan together, but will still establish contact with Ancora.
I got an idea for a "Post War Arc" but lets leave it for now
Basically what I have in mind is, post war arc will take place 5-7 years after the main series. Humans and "Non Humans are starting to coexist, including vampires, but there's still conflict present. Ancora I think will have a new principal after Elisa steps down.
Meanwhile, Jill and Triela look up Yu and Yuki in Japan. They request Yu's aid as Ergon is in some sort of trouble. Since Yu was close to Evelyn before, and most of Ergon know him, the figure he might be able to do something.