The second check in took quite some time, but we had plenty of time to go pick up our free rental phones, and then head out to the sun to try to get enough light to reset our body clocks:
Japanese domestic security was a breeze, and once inside we got access to some surprisingly good airport food (though rather ungenerous in portions --- I had to order 2 meals to feel decently full), and met a bunch of mathematicians who were going to Sapporo for a conference.
Arriving in Chitose at 8:10pm, we were glad that we had opted to stay at Chitose airport's Hotel Com. Not only did it save a 45 minute ride to the Sapporo while wrestling bike boxes (not to mention searching for our hotel), the staff spoke English, and was happy to store our bike boxes and other luggage while we were away on tour.
I looked at the weather forecast for the next couple of days, and saw that it called for rain, with a 50% chance of thunderstorm on the 28th. I thus made the executive decision to scrap our original plans and spend a day exploring Sapporo instead, shifting the city exploration to the start of the trip rather than to the end.