The Doomed Earth - In Our Star

When the destruction of Earth causes a time rift, one ship is thrust
back in time to decades prior. The semi-disgraced naval officer Kayl
Owen is sent from the Earth Guard ship Vigilant to investigate. He
finds one person alive, one person whose DNA analysis reveals to
have some non-human DNA, a person who his superiors say isn't
human.
That's not how Kayl Owen sees it. He thinks Lieutenant Genji of the
near future Unified Fleet — the future successor of Earth Guard —
is every bit a person. And more, the knowledge she brings from the
future might hold the key to saving Earth from destruction.
Owen, Genji and everything they know is deeply threatening to a lot
of people, and the two of them need to survive each day to get to
the next and save the future for everyone. But will changing Earth's
future erase Genji?