Basically, in some made-up world of 'fantasy' the King of a powerful Empire makes a deal with a magic entity to open a portal to another world to further his already extensive borders and further his plunder via conquest. Without knowing fully what they're doing they open a portal to the current age in a major metropolitan area (like New York City) for example. Thousands of legions of ancient warriors (however you like them, legionaries or knights, throw some dragons in there if you want, whatever) storm out of the newly created gate and begin to pillage and kill, claiming the new world as their own. Obviously the military is dispatched and the invaders are no match for modern weaponry, they're pushed back through the gate with almost all of the invading force killed. In the world of fantasy the modern military is able to easily capture the gate and fortify it, preventing another attack on their world.
Unsure what they're dealing with exactly the military forms a small Long Range Recon Patrol group to gather intel on their new enemy. And this is where I was hoping to start. Your character could be anyone you want from the fantasy world. Injured soldier, nobles, villagers and so forth. It's a basic "Stranger in a Strange World" sort of thing for me, who will play a character in the LRRP and all the NPC's in it, along with the natives having to deal with the overwhelming technological advances they'll witness that to them will seem like unstoppable magic from things as simple as a flashlight or as extreme as an attack helicopter.
So that's the basic idea let me know if anyone is interested.
I figure High-Casual to Low-Advanced level. I can incorporate romance too if you want. I can do MxF or FxF for this.