Big travel tip for everyone if you’re flying domestic in Japan: ask for an upgrade at the counter.
I’m not sure if they still do it now, but when we were traveling in Japan a lot, my mom and I discovered this amazing little trick. An upgrade to business class is a mere $10 extra and first class is somewhere around $30 extra. Absolutely worth it if you’re on at least a 2 hour flight, like from Osaka to Hokkaido.
One caveat is that you might need to be flying with Japan Airlines (JAL) to get this upgrade, but it’s still worth trying with whichever airline you’re flying with. JAL, though, is amazing when it comes to first and business class. Chairs that kickback a full 180-degrees, a bajillion customization options, and free food and wine. Surround-sound and personal TVs, of course!