The Snow Country Trail is a hiking course that covers 280 kilometers through towns in three prefectures between Niigata, Gunma and Nagano. You don't have to do the whole thing but can pick and choose which sections interest you or suit your ability. There are plenty of things to stop off and do along the way as the trails head down into the valleys and towns, as well as up to the peaks. Stunning scenery all around and you are never too far away from an onsen either, so after pounding the trail all day you can recuperate with a good long soak.
The Snow Country Trail website has the route maps for each leg though it is only in Japanese at the moment.
Some sections run through national parks and delicate ecosystems so camping is prohibited in those areas. Also a significant portion of the trail traverses steep terrain where finding space to pitch a tent would be almost impossible. That being said, I did happen to spot the occasional flat bit of land to pitch my tent on, although far a few between.
The sections that i have hiked did not seem that dangerous to me.
As far as "getting off the trail to the nearest town in an 'emergency'", again the answer varies depending on the section of trail. There are a few hiker's huts spaced out along much of the trail, but there are some sections that are remote, and as much as a day's hike away. As a general rule when you are day hiking you should always be prepared to spend the night out in an emergency. That means carrying at least an emergency blanket, spare food, and a head torch. If multi-day hiking then you should have a first aid kit as well as an extra 2 days of food. In another countries an emergency locator beacon has basically saved my life when injured out in the wilderness, but I have no experience with them in this country. Where ever you go hiking you should tell some one your route and when you expect to be back. I have personally been involved in a rescue on one section of SCT and I will tell you that the response time is on par with anywhere else in the world.
If you have specific questions about a section that I have hiked I would be happy to answer them.
When you went on the trail, did you happen to hike the entire thing? How were the 'dangerous' portions of the trail? Would getting off the trail to the nearest town in an 'emergency' be possible in a reasonbly short amount of time on foot? Are there frequent emergency stations along the trail?