On last viewing, the "white" seems to be "blossoming" even as the black receeds lower and "solidifies". It also occured to me that having more black on the lateral surface makes it seem that it's more male in conformation, regardless of the actual gender; just like how women tends to "shed weight" in a flattering black dress
Hmmm... "Fatter" Koi might actually look better when clad in black
