A Legionnaire’s Guide to Love and Peace by Emily Skrutskie

In this charming fantasy with a swoony friends-to-lovers romance, two soldiers must choose the futures they want in the wake of a last-chance hookup on the night before the world was supposed to end.

A one night stand before their one last stand.
On the eve of the battle that will decide the realm of Telrus’s fate, Katrien takes a hard look at her prospects. A mere legionnaire, she and her spear will be at the fore in the morning, facing off against the Demon Lord and his wretched army, and it’s all but certain she’ll perish in the fight. But if the end of the world is mere hours away, there’s no reason not to hook up with her handsome, dedicated battle partner, Emory—despite any antifraternization policies their centurion may have in place.
Only the world doesn’t end the next day. Instead, an insufferable prince raised in hiding comes out of nowhere with a plucky band of heroes, defeats the Demon Lord, and seals the rift to the hellish plane. The realm is saved. The war is over. And Kat suddenly has a lot more future than she knows what to do with.
But while the Demon Lord has been destroyed, peace is still a long march away. When Kat inadvertently catches the eye of the prince, she, Emory, and the rest of their motley unit are pulled to the fore of the formation—and the heart of the danger—as the army embarks on one last campaign.

As Kat and Emory work to secure a lasting peace, they’ll have to decide what they want their futures to look like—and if there’s room for love at the end of the road.