JR East-South Hokkaido pass

Hi, I am interested to do the tateyama Kurobe route one day I am in Japan. I want this to start from Nagano. I will be buying the JR East-South Hokkaido Rail Pass as we will be doing most of our travel towards northern Japan and Hokkaido.

The JR East-South Hokkaido Rail Pass covers Hokuriku/Joetsu Shinkansen only up to Sakudaira station. My plan was the buy a seperate ticket from Sakudaira to Nagano station in advance but sometimes the trains from Tokyo to Nagano donft stop at Sakudaira station and I am worried if I buy a ticket in advance for Sakudaira-Nagano it wonft let me tap out at Nagano as I didnft do the first tap on at Sakudaira station.

I know it will be possible to get down at Sakudaira station, exit the gates and enter back with the tickets I purchased in advance and catch a train to Nagano station and I have to do the same thing back on return but this will waste time and I prefer the express train from Tokyo - Nagano with only 3 stops that doesnft include Sakudaira. Could you please help find a better way. Thank you for your help.

Same question was answered here:
https://www.japan-guide.com/forum/quereadisplay.html?0+179574