[A]mong Saichō’s later followers, the traditional T’ien-t’ai “perfect teaching” (engyō) based on the Lotus Sūtra was fused with Mikkyō in the “one great perfect teaching.” Their writings recapitulate Saichō’s move to incorporate all teachings within the Lotus, but in esoteric terms. That is, rather than encompassing Mikkyō within the framework of the one vehicle of the Lotus as Saichō had intended, Taimitsu developed an esoteric reading of the one vehicle that tended to subsume the Lotus within Mikkyō, a tendency especially evident in Annen’s writings. In any event, the two traditions became inseparably intertwined and came to share a common vocabulary. Medieval Tendai hongaku thought would emerge in large part as an attempt to reinterpret traditional T’ien-t’ai/Tendai doctrines through the lense of an esotericized sensibility. (Page 24)