The question is an interesting one - What is "Traditional" Reiki?
In the United States, as well as in many parts of the world, "Traditional" Reiki has been previously defined as that form of Reiki passed from Usui to Hayashi to Takata to Furumoto, and hence, to other "traditional" Reiki Masters, each of whom can provide certification and written lineage. This was generally accepted as true until quite recently. Both logic and history now call this into question. Even the history of Reiki as taught by "traditional' Masters included the fact that Usui, Hayashi, and Takata each trained a number of Masters [between 18-22 each], hence, logically there are many traditions which trace directly to Usui which do not include the "Traditional" path or lineage.
Moreover, there exists in Japan today a Reiki tradition, with direct lineage to Usui, which does not include either Hayashi or Takata or Furumoto. In one sense, "Traditional" Reiki would only include those Masters in that tradition. Several distinct features in TJR [Traditional Japanese Reiki] depart from the "Traditional" form of Reiki which stems from Takata. These differences are in both practice and teaching. This presents a dilemma to a serious traditional Usui Reiki practitioner.
I have read much of the available information on the history of Reiki. The weight of the evidence clearly supports a position which shows all Reiki Masters having some lineage back to Usui, regardless of tradition. Additional information suggests that Reiki [not known by that name] has existed as an energy practice in other cultures as well, some of which passed it by attunement; others required lengthy study and self -discovery to practice it. Although there were variations in method and teaching, this would mean that the practice of passing healing energy by a hands-on method, or distance method goes back several thousand years, enjoying periodic revival as a healing method. Usui rediscovered the method and named it "Reiki".
Therefore, I understand that, when I call myself a "Traditional" Reiki Master, I am historically in error, yet correct by the tradition which attuned me, and correct in the manner that most people in my country understand "Traditional Usui Reiki". I assume that sometime in the future, when the correct historical information is known more widely, that I will simply say that I have been attuned in several traditions, one of which traces back to Usui through Furumoto, Takata, and Hayashi. It is obvious to me that Usui meant for Reiki to grow and be modified. It is equally obvious to me that each Reiki attunement that I receive adds to my healing skills, as well as to the totality of the Reiki energy which I can share.
What is important is the Reiki energy; the Reiki lineage and tradition will vary among Reiki Masters - the basic Reiki energy will not.
For a wealth of information on Reiki history, please visit Rick Rivard's HomePage.