In MonGirl Sexpedition, Jack lived a simple life, but all of that ended on his birthday. He finds himself in an unknown land with lots of monster girls and a task from the Goddess herself. Jack will meet quite a few attractive girls along his journey. Will he become friends with these girls, or will something more happen? That is up to you. If you increase your power, you'll receive the ultimate reward. Let's just say this is a reward that will put a smile on your face.