User blog comment:Marijuanna/Rare Zanpakutou/@comment-3177945-20130117165953/@comment-6011391-20130118131529

this may give rise to another reason why kenpachi and kurosaki do not have their zanpakutos in a sealed form, other than because of their immense spiritual pressure. we can also see that zangetsu has constantly change its appearance from time to time which i can suggest that zangetsu is purely part of ichigo's soul. unlike the other shinigamis, ichigo is unique. that is why zangetsu changes shape following ichigo's development. as for shunsui and ukitake, my theory is initially they only have one asauchi, then as they were imparting their souls into the asauchi, it might have been massive thus they divide it into two. this is similar to that of coyote stark. whereby by dividing his power into two, it is easier to control. well, these are just my theories.