It is preached in the Lotus Sūtra … that the merits of all the sūtras preached during the period of 40 years or so are all stored in the one Lotus Sūtra and the threefold bodied Buddhas in all the worlds throughout the universe are all Buddhas in manifestation of the one Śākyamuni Buddha. Therefore, “one Buddha equals all Buddhas,” and the two characters of myō and hō include all Buddhas. Accordingly, the merit of chanting the five-character daimoku of the Sūtra of the Lotus Flower of the Wonderful Dharma is enormous indeed. On the other hand, the 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, Writings of Nichiren Shōnin, Faith and Practice, Volume 4, Page 20-21