There has been much confusion regarding the resemblance of Serama to Japanese bantams. Unfortunately to the extent that Serama are being passed at exhibition for being "poor Japanese specimens". This should not be the case with distinction between the breeds being very clear.
Here is a drawing I have made to show the shape differences in Serama and Japanese bantams. Of course these are females however males are much the same allowing for natural sexual differences such as ornamental feathers and larger combs. Silkie / frizzle serama and Japanese should also follow the same outline but posess a different feather structure.