A Sea of Endless Light by Chani Lynn Feener

Fox Axford has been tasked with capturing a feared thief who has been terrorizing the Hild Empire, not flirt with the impassive captain he’s been unlikely paired with.
When Fox is assigned to the Hild case by the Intergalactic Police Force, he doesn’t anticipate it taking very long. He’s known for his wits and charm and is confident enough in his abilities to have this thing solved and closed before the week is through. Except, he didn’t account for how distracting working with Captain Jiro Arc was going to be.
Jiro Arc has a secret he’s been keeping all his life, one that he’s never wanted to share with anyone. Until the day Detective Fox appears.
Having lived quietly climbing the ranks of the Hild Comets, Captain Jiro is used to rebuffing attention with his steely disposition. All of his efforts seem to have the opposite effect on the detective, however, who only seems more and more interested in Jiro and his personal life as time goes on. Their main task is to find the mysterious thief Shilling and bring him to justice, but Jiro has an agenda of his own, one that might ultimately lead to him betraying Fox, whether he likes it or not.
Fox grows even more conflicted after meeting the thief they’re after. Shilling isn’t at all what he expected, and when he finds himself sympathizing with the enemy, Fox is forced to acknowledge that there may be things he doesn’t yet know or understand about the vast universe, and the people living in it.