[T]he titles of various Buddhas and sūtras are expedient teachings, which were opened to reveal the true one by the Lotus Sūtra. The five-character daimoku of the Lotus Sūtra is the one that opened them to reveal the true teaching, and therefore we should chant the daimoku of the Lotus Sūtra.
Shō Hokke Daimoku-shō, Treastise on Chanting the Daimoku of the Lotus Sūtra