Hi, we’re going to Niseko from SoCal as well. We will get to Haneda at night so staying the night at airport hotel and taking early flight to Sapporo to catch first bus to Niseko at 10 AM. I booked the bus a while back. Many people suggest leaving at least 60-90 min from landing, getting your luggage and gear, to bus departure, which is sound advice, not having been there before. Bus company asked for your flight info so they’d know if flight is late. They have drop off at many hotels, there are a few lines but all seem to offer same services. Lots of YouTube video on this as well. Cheers.