7-8 day trip in Japan including Sapporo – Recommendations?

Hey guys, my friends and I noticed we had an extra week of break than what we had previously thought this time next year so we decided to add Japan into our trip. Problem is, Japan is a big country (obviously) so it's impossible to see everything in 7-8 days.

One person really wants to go to Sapporo for the trip, and because we are all from Australia we are eligible for the free domestic flights, so our intention is to fly to Tokyo and then to Sapporo.

We'd also love to get a mix of the traditional/pop culture and scenery which seems impossible to do in about a week so I'd really appreciate some pointers,

Seeing this where would you guys suggest we visit outside of Sapporo in Japan? Is there anything specific in the area during January?

Would you guys recommend a brief trip through the entirety of Japan or to have a week in a specific area then come back another time to experience the rest? We'd love to get a lot of the big cities in – but we wouldn't mind skipping if we get to experience more things.

Thanks!

by Buttercookies97