I beg to differ with the first responder.
Marinating in an agent like butter milk is NOT OK for two straight days. Marinating makes meats more flavorful and tender because the meat is somehow "broken down" by the marinade and if you leave it to marinate too long, it will be mushy meat. The texture will completely turn you off. It will just keep breaking down the tough meat fibers. I know my explanation is not in technical or scientific terms but I know I am correct.
I would remove the chicken from the marinade and wipe it off and store it for one more day in the fridge. 2 days in the fridge is fine for uncooked chicken.
Or, take it from the marinade and bake it as is and then use the cooked chicken on salads or for sandwiches another day and make the fried chicken another day.
But don't leave it soaking for much longer. I learned the lesson the hard way once!
You could also remove it now, wipe it off and then tomorrow re-dip it quickly in some fresh marinade and then in whatever crunchy topping you are using. That way tonight it stops the process of tenderizing but tomorrow you still get the benefit of the buttermilk as a way of holding on the crunchy stuff.
Have fun with your friend!