Hollow Regalia, Vol. 6 (light novel‪)‬

Three years after the Ploutonion closed and the world narrowly escaped destruction, humanity is slowly recovering. Although Yahiro and Iroha saved everyone, the pair’s whereabouts are unknown. One day, peace is disrupted when Galerie Berith receives notice that Moujuu have reappeared. Meanwhile, on a nameless island in the south, Yahiro and Iroha have been enjoying a laid-back lifestyle when a mysterious girl washes up on their shore. She is wary of Iroha yet seems quite familiar with Yahiro and the reality of their world. Then, suddenly, monsters attack! Not the Moujuu, but a new threat that appears to be…angels?!