LOL! Dick, look what trouble you've gotten me into.

... Folks: Recall that Dick called me a "student". A very accurate term! I'm a learner...And, I've got a lot to learn!
Aragorn: Yes, there is temporary Sumi that shows up in baby koi. It is probably an adaptation from the wild... a type of protective camouflage for youngsters, not unlike the way black and gray tones on very young comet goldfish will fade away revealing a standard orange-red goldfish. Check the thread I started called "A Rainbow of Showa", and look at the one I call "Pumpkin". There is absolutely no resemblance between her nearly black face in Fall '04 and her face in Fall '05.
PapaBear, I'd really like to see a photo from one month earlier to compare and see what direction things are going, but even then I'd likely not be able to give you reliable advice. First, the dark blotches next to the dorsal "feel" like permanent Sumi to me. I expect it will consolidate and the edges become more defined. But, the pic is not very good for really saying. On the other hand, the darker "wash" of sumi that looks like it was lightly brushed on along each side of the dorsal fin has the look of temporary Sumi fading away. The Hi will become more pure as that "over wash" of Sumi disappears. The deep Sumi patch will then stand out even more...I think.
The blue-gray area is the more interesting part, because I've seen areas like that develop in several ways. It is not what I call "baby Sumi", which is superficial. It is Sumi deep in the skin layers. I've seen fish where the area becomes white by the time the fish is nisai, only to have the Sumi rise up at age 4 or 5 and cover everything. Sometimes the area just stays white ... but maybe it returns at age 7? (LOL) [I've not kept any long enough to say from personal experience.] In other fish it is Sumi forming now and beginning to "rise" to the surface; and in still others true Kage shadows are formed, which may be permanent or very slowly become consolidated Sumi. I'd like to think you have some Kage there, just because it would be very attractive if it turned out that way.

I kinda feel there is a chance of staying Kage because of the way the Sumi fills the areas under the scales... gives an impression similar to young Asagi. But, this is a very young Showa. I really think you have to be familiar with offspring from the pairing that produced it to do much more than guess at that size and age.
I enjoy guessing about little Showa because whatever happens, I learn from it. I hope you keep that little thing and post a pic in Spring when ready to go back in the summer pond. Then we can see how the winter treated it. Then more pics at the end of summer as nisai, which is when we can really get an idea of what is happening.