QUESTION: Is there any sūtra that compares the superiority of the Lotus Sūtra and the threefold sūtra of the Great Sun Buddha?

ANSWER: It is said in the chapter on the “Peaceful Practices” of the Lotus Sūtra: “It (the Lotus Sūtra) is the supreme of all sūtras.” This tells us that Śākyamuni Buddha Himself recognized this sūtra to be the most superior among all the Buddhist scriptures. In stark contrast, nowhere in the thirteen fascicles, namely, the seven fascicles of the Great Sun Buddha Sūtra and three fascicles each of the Diamond Peak Sūtra and the Sūtra of the Act of Perfection, do we find even one phrase or one line stating that these three sūtras are superior to the Lotus Sūtra. There is only one line found in the Sūtra of the Act of Perfection stating that this sūtra is the “king” of this three-sūtra group. However, this merely means that it is the “king” of the threefold sūtra of the Great Sun Buddha, not the great “king” of all the sūtras preached by Śākyamuni Buddha in His lifetime. It is like calling the king of Japan, the “great king.” It means that he is a great king but does not at all mean that he is greater than the kings of China or India. The Lotus Sūtra, however, is not only the “king” of all the sūtras Śākyamuni Buddha expounded in His lifetime but also the “great king” of various sūtras preached by all the Buddhas manifested in all the worlds all over the universe throughout the past, present, and future. It is like the Great King of the Brahman Heaven, a great king superior to all kings including the various small kings, the Wheel-turning Noble King, the Four Heavenly Kings, Indra, and the King of Devils in the Sixth Heaven.

Ha Ryōkan-tō Gosho, A Letter Refuting Ryōkan-bō and Others, Writings of Nichiren Shōnin, Volume 5, Page 58-59