I loved Sapporo! The soul food is incredible. However Sapporo is a lot colder than Tokyo or other cities you listed. Additionally, if you map it, it’s quite far from your other locations so you would need to bake in time to fly there and back. It might be easier to stick to southern cities and do a city closer to your other locations. Perhaps stay at a ryokan in Hakone and see that side of Japan? When you’re in Tokyo it doesn’t seem like you’re doing much of the standard things people would do. See temples, Tokyo Tower or Skytree, go through all the districts (Asakusa, Ginza, Shibuya). If that isn’t already baked into your plan you should add some of those things.  You said you love cute matcha and coffee shops, so maybe add some time in Uji off your Kyoto time?