Taken By the Wanderer by Sarah Blake

Wanderers are meant to kill any human they meet. What if he wants to claim her instead?

The future seems hopeless for Researcher Rae Addams. Instead of thriving galaxies and lively planets, each planet is in ruin, and her people have yet to find another lifeform. Humanity is struggling, the future is bleak, and their citizens are forced onto suppressants to keep them unemotional and detached. But when Rae crashes on a planet with an alien warrior, there is no suppressant in existence that could keep her from wanting him.

Argo is a Wanderer, charged with scouring the universe to find a cure to his people. Part of the last generation to be born, he was raised to hate humans for the bioweapon they unleashed on his planet. When he meets Rae, for the first time in his life, he hesitates before the kill. Stranded on a deserted planet with the enemy, he begins to wonder if the infuriating human who makes his body come alive might be just what he has been searching for.