The term "Derivative" is sometimes difficult to explain and conceptualize. The overseas often call such characters "fan mades" or "fan made characters", but refer to them as different characters in their own right. However, in the Japanese fandom, the character is often considered a variation of the original. Therefore there is often disparity between fandoms as to how 'Derivatives' are treated. This also means official derivatives like "Racing Miku" or "Snow Miku" can also be considered a variation of Hatsune Miku and at the same time not Hatsune Miku herself. This way, derivative versions of a character can exist side by side in any promotional media base medium with the original character as two different entities to each other, rather than just alternate outfits.
