Speaking to the GF is how you get non NTR, the other are events that happen as you go. Its not really a survival game for the most part. Just keep enough food to not starve, and you dont need to eat everyday so your food lasts longer then it says. If you have food, you don't need to go explore since you risk getting hurt for nothing.
You have 3 NTR routes, Shota Hypnosis, Old man netorase/sharing, and the convenience store big dick who just takes your girl. There are route guides posted if you have trouble getting one. You can have a couple happy ends by just surviving to the end or escaping in a car, ect.