We finally did the Tateyama Kurobe Alpine Route and saw the famous snow corridor! This route is only open from mid-April till end-Nov every year and the best time to see the snow corridor is between April to June. NGL but it's quite a tiring route and you can see I got visibly more tired towards the end of it but worth the snow corridor experience.
I've provided some useful links below to help with your planning:
Information on the Route: www.alpen-route.com/en/
Infographic on the Route: www.alpen-route.com/en/timetable/
Car Forwarding Service: www.tateyama-traffic.jp/English_page.html
We paid JPY 10,940 per pax for a one-way ticket between Tateyama Station and Ogizawa Station. Don't lose the ticket as you'd need to scan it to access each mode of transport along the route!
Kamikochi Hotel: www.kamikochi-hotel.com/
Let me know in the comments if you have any questions!