just heard from one fm radio saying that starting 1st July 2013 no need visa to visit japan, just use the passport with the embedded chip and u can go in for 90 days

last time i came across this discounted domestic air flight ticket in japan for foreigner
http://www.japan-guide.com/e/e2364.html

i didn't really go understand how does it work as i didn't travel to sapporo tat time
u may try to read n understand, maybe u can get cheaper flight

or u may try to buy a 7days or 14 days JR pass, travel from tokyo to sapporo using shinkansen (u may need to switch station)

good luck hunting the info