Voices of a Distant Star

It is 2046 when a mysterious alien force begins their annihilation of the human race. Leaving behind the one person she loves, Mikako joins the interstellar battle as a pilot. As Mikako flies further into space, her only connection with Noboru are text messages sent from her mobile phone. And so - while Mikako risks her life to save mankind - Noboru waits. The two lovers, worlds apart, desperately strive to remain connected as the gap between them widens at a frightening pace. Source: crunchyroll