Survivor Girls Sanctuary

Monsters show up out of nowhere and the world ends, the way it always seems to in these things. You play the guy left to deal with it, which mostly means fighting through waves of them while picking up girls along the way.

The setup is thin but functional: apocalypse hits, protagonist fights back, survivors join him one by one. Nothing more complicated than that.

Combat is the main loop, monster encounters that clear the way to rescuing girls, who then stick around and grow closer to him as the game goes on. It's a straightforward push-forward-and-collect structure dressed up in a fantasy-monster setting, with the relationship side running parallel to the fighting rather than replacing it.