Hentai Turret Girl (AppID: 2253150)

In a post-apocalyptic world, a woman must scavenge to survive. But she's not alone; she has a turret implementation on her back that helps her defend against the dangers of the world. This is a romantic visual novel about her struggles to find love and acceptance in a hostile world, with a Match3 Jewels mini-game to break up the action.

World:
In the year 2xxx, the world was attacked by a force of darkness unlike anything anyone had ever seen before. These monstrous creatures devoured entire cities, leaving nothing but destruction in their wake. The few people who survived were left with no hope, and many of them soon became part of the invasion themselves. No one knew where these creatures came from, but they brought about the end of the planet as we know it.

She:
The woman's childhood was spent in a world that was on the brink of destruction. The monsters had already invaded and were threatening to annihilate human civilization. In order to fight them off, the woman had a turret implanted in her back. This meant that she had to undergo arduous training from a young age, without any love or support.
Despite all the odds, she managed to escape from the monsters. However, she failed in her main mission: to find a new home for humanity. Now that the world had ended as we knew it, she was trying to make her way back home. It was a long and difficult journey, but she was determined to succeed.