Dog Days 3 eye catcher Adel cosplaying as Valerie.

well episode 8 is out and it was pretty heartwarming but i think this is meant to more or less establish or hint that Valerie and Adel did settle down with each other which is why Cou can refer to both of them as her ancestors. a sad story of Valeries sister being the princess who established the peace that currently exist but at the cost of her own life. Hina and her brother are surprisingly older than they appear. apparently being soaked in demon blood has them essentially immortals and can never die according to them. would explain why they know so much despite how young they look.