Koi is an irregular marking present anywhere on the Xunari, either symmetrical or asymmetrical, and can have a hard, soft, or textured edge. It cannot be a single large patch of colour, and very small patches must be limited lest they mimic barring or ember. These patches are solid, meaning they have no holes within them unless modified by ticking, and they can be either darker or lighter than the base coat.
In its heterozygous form (K k), it can only be one colour or tone but when in homozygous dominant form (K K), this can increase to up to three different colours, which can differ in light or dark. Unlike Marozi, this difference in coloration is per-patch, not within a patch. One spot cannot be multiple colours, though there may be moderate overlap between spots.
When affected by artifice, either one of the colours (in heterozygous or dominant) or all (in dominant) may be the affected colour.
Koi can also be patchy and follow the fur for its edges instead of being rounded.