Family and group may prefer rental house or condominium with kitchen to hotel.
In Niseko ski resort area, its easy to find condos. But how about Sapporo and other area?

Sapporo

In Sapporo, the condominiums commercially prepared are few. You’d better to search in
airbnb(E)
where you will find some unique choices such as the Samurai House.

Other Area

Japan Hotels Official Website Directory(E)
can be searched by the keywords such as Cottages, Lodge, also Pension, Auberge, Youth Hostels, Capsule Hotels, Public Inn,Tourist Home, Japanese Inn etc.are listed as keywords.

“Self cooking available” search can be done at
YadoClip,
a Japanese website of the above JHOWD. Cottage and Lodge are usually located in camping site or resort, so they are outside cities.