Lovely pictures, thanks! John your "Unknown" is a Sycamore Maple, Acer pseudoplatanus. If it's not grafted it may just one of the many pretty seedlings that leaf out red/orange in spring. You had better name that Mikawa seedling before someone else does! :) Just joking of course. It seems like there are a gazillion of these around now. Nice to see someone's 'Mino yatsubusa' doing well, mine had a hard winter, which included getting a couple of cows get into the yard, one of whom ate half of it. It's coming back but reluctantly. Speaking of sycamore maples, here is one of my selections that I planted out this year. It starts out quite a dull olive green but then develops into this as the leaves mature. I like it a lot, we'll see how it does in this sunny spot.