Shhhh....it's a secret

"The equation of Nichiren with the original Buddha is not easily reconciled with Nichiren's own clear expressions of reverence for Sakyamuni as "parent, teacher, and sovereign" of all living beings, and this particular strand of Nichiren Buddhist thought has been much criticized by other Nichiren schools. In recent decades, it has come under attack for lack of basis in Nichiren's writings by those sectarian scholars of Nichirens hu intent on purifying the Nichiren corpus of apocryphal works as a basis for establishing a normative doctrine, a project in which the present-day inheritors of the Fuji lineage - Nichiren Shoshu - have evinced little interest. But authenticated writings of a founder are not the only basis upon which religious traditions have, historically, chosen to argue tier authority. Scholars of the medieval Fuji school, like the Tendai lineages of their day, based their interpretations of doctrine and their claims to legitimacy less on original texts than on secret transmissions, a hermeneutical approach that its modern descendents have in large measure inherited." 

{Original Enlightenment and the transformation of Japanese Buddhism, by Jacqueline Stone Ph.d.,}