Shiragawa-alpine route - Karuizawa to tokyo

I plan to visit Tokyo early April 2017. In Tokyo stay 1N plan to go shiragawago for 2N then alpine road 1N and Karuizawa 2N back to Tokyo 2N.
I can't find any train or bus from shiragawago to Alpine route? And from alpine route to Karuizawa?

Is is a good time to visit alpine route on 10 april? What is the chances seeing cherry blossom?

Thanks for all the inputs in advance. Xoxo

Tokyo to Shirakawago http://www.japan-guide.com/e/e5953.html

Going to Alpine Route http://www.japan-guide.com/e/e7551.html

Alpine Route to Karuizawa - See Japan Guide links as posted

Karuizawa to Tokyo http://www.japan-guide.com/e/e6031.html

Alpine Route Season - http://www.alpen-route.com/en/

Cherry Blossom -
http://www.japan-guide.com/blog/sakura16/
http://www.kyuhoshi.com/japan-cherry-blossom-forecast/
http://sakura.weathermap.jp/

Is is a good time to visit alpine route on 10 april?

If you plan to walk the snow corridor, be sure to check the 2017 Alpine Router report.
In 2016, the snow corridor was open to pedestrians from April 16 to June 22.

Sorry, ought to be "Alpine Route report"