Orc Bastion

A newly drafted soldier gets bound soul and fate to the orc warrior who's supposed to be his enemy, and things go from there. Reyn didn't sign up for this war so much as get thrown into it, and now his survival depends on a monster he's expected to trust.

Reyn and Rok are stuck together until death, which turns out to be a decent foundation for something between a war campaign and a relationship. The two of them, along with whatever allies they pick up, are meant to broker peace between mankind and hell's denizens, one battle at a time.

Combat runs turn based, JRPG-style, with a growing party you build out as you go. Along the way Reyn gets to know the orcs, demons, and monsters around him a lot more intimately than basic training probably covered.