During winter season there are several overnight bus from Kansai (Osaka and Kyoto) area to Hakuba area, catering to skiers. These bus services are seasonal and usually run as a charter bus by various tour companies. Tickets are sold as individual passengers, just like scheduled bus service, but often tickets are sold through tour companies only. Usual websites to search trains and bus schedules will not show these type of bus services.
Websites are in Japanese only and often reservation by phone calls are by Japanese only. One way fares are somewhere form 5000 yen plus. Departing Kansai area anywhere after 9 p.m. and arriving Hakuba 6-7 a.m. next day. If you read Japanese, some of tour companies with such bus services are:
http://bus.otokuski.jp/kansai_hakuba.html
http://www.upon.co.jp/nature/ssw/
http://www.snowclub.jp/bus/kansai_hakuba.html
JR used to have various overnight trains form Tokyo and Osaka area to ski areas during ski season back in good old days of peak of bubble era. However, as ski become less popular and people shifted mode transport to driving, those winter only overnight ski trains disappeared.