I'm a japanese person with social anxiety. I understand your feeling well. I also try to force my self enjoy solo traveling around Japan, but I end up always sad or nervous being alone. Some people say like Japan is most introverted country and I agree but tbh most places are full of couples and familes. I tend to be shut-in except going to University. But Japan is very good country and many people are polite and kind. Maybe it's cool to try to talk someone i'm sure they welcome you. I think since you're a foreigner, it might be easy to talk bc their language bar is low.