I discovered soy sauce and vinegar some years ago when I had an illness that severely restricted my diet. I was, for several weeks, eating mostly rice. Not that I was unfamiliar with soy sauce and rice. I had used soy sauce on rice before. However, blending it with vinegar had not occurred to me until I found myself in need of something to make the rice more interesting.
The combination was very good. I tried malt vinegar, rice wine vinegar, balsamic vinegar, and red wine vinegar. I suspect that I would have become quite an expert on vinegars, but my digestion got better and I was able to expand my diet.
What I learned about soy sauce and vinegar stuck with me. Now, when I chop up some barbecued meat to use in a sandwich or wrap, I chop it fine and put it in a sauce pan. To this I add a bit of soy sauce and vinegar. It is a light sauce to add moisture to the chopped meat.
I have yet to get going with marinades, but I see real potential in soy sauce and vinegar as a base. That, and beer. These just seem right. I have visions of marinades including a cornucopia of vegetables and fruits. Herbs and spices. Marinades and sauces.
Yes, I have only just begun. I see great adventures ahead.