Grand Master Dengyō, the primogenitor of exoteric and esoteric Buddhism in Japan, has said in his Hokke Shūku (Outstanding Principles of the Lotus Sūtra): “The canons of other sects, too, preach some ultimate reality, which is the mother of Buddhahood. However, those scriptures have motherly love but no strictness of the father. Only the Tendai Lotus Sect, with both its strictness and love, is the parent of all sages, wise men, those who have much to learn and nothing to learn, as well as of those who aspire for enlightenment.”

Kaimoku-shō, Open Your Eyes to the Lotus Teaching, Writings of Nichiren Shōnin, Doctrine 2, Page 76

Two boys named Tokushō and Mushō donated “rice cakes” made of sand to Śākyamuni Buddha, who was practicing “begging for alms.” Upon their death they were reborn as Emperor who governed one-third of the Jambudvīpa according to the Buddha Dharma. Bodhisattva Māṇava attained Buddhahood as merit for offering five stems of lotus flowers to Burning Light Buddha. He is none other than Śākyamuni Buddha.

It is preached in the “Teacher of the Dharma” chapter of the Lotus Sūtra, fascicle 4, “If a person who seeks the Buddha Dharma presses his palms together in My presence and extols Me with numerous verses of praise for as long as a kalpa (aeon), he will gain innumerable merits because of these praises of the Buddha. If he praises the upholder of this sūtra, his good fortune will be even greater.” This means that the merit of helping the practicer of the Lotus Sūtra, who is given the cold shoulder by the people in the Latter Age of Degeneration, is greater than giving offerings to the Buddha for aeons.

If you are wondering who would have said such an outrageous thing, it was stated by our Lord Preacher Śākyamuni Buddha Himself. It is up to you whether or not to believe this.

Ueno-dono Gohenji, Reply to Lord Ueno, Writings of Nichiren Shōnin, Followers II, Volume 7, Page 3-4

All the worlds throughout the universe, therefore, are the dependent reward while all living beings are the principal reward. The dependent reward is like the shadow of the principal reward. As there is no shadow without a substance, there is no dependent reward without the principal reward. However, the principal reward is also created by the dependent reward. We should know that the eyes are created by the east, the tongue by the south, the nose by the north, the body by the four directions, and the mind by the center. Accordingly, when the five sense organs of a living being are about to be destroyed, it is inevitable that the earth in four directions or in the center trembles. In other words, when a country is about to be destroyed, there will inevitably be such omens as the crumbling of mountains, death of plants, and the drying up of rivers.

Zuisō Gosho, Writing on Omens, Writings of Nichiren Shōnin, Followers I, Volume 6, Page 123

Having faith in the Lotus Sūtra involves suffering and punishment by the shogunate. There is no doubt that the moon wanes and waxes and the tide ebbs and rises. Though at the moment I endure punishment and suffering, they will return to me as merit. Why would I lament a joy such as this?

Toki-dono Gohenji, Reply to Lord Toki, Writings of Nichiren Shōnin, Biography and Disciples, Volume 5, Page 11

Śākyamuni Buddha predicted in the Nirvana Sūtra the condition of the world in the Latter Age: “Slanderers of the True Dharma will be as numerous as particles of the great earth while those who uphold the True Dharma will be as small in number as particles of the soil on a fingernail.” How true these words of Śākyamuni Buddha are! The present condition of Japan is exactly as predicted by the Buddha.

Ha Ryōkan-tō Gosho, A Letter Refuting Ryōkan-bō and Others, Writings of Nichiren Shōnin, Volume 5, Page 62

In Hinayāna sūtras, the principle of inactive nirvana (ultimate goal of Hinayāna Buddhism to attain emptiness and tranquility) is the king, and wisdom is the king compared to observance of Hinayāna precepts and practice of Hinayāna meditation. In Mahāyāna sūtras, the principle of the Middle Way (non-duality) is the king. Also the Flower Garland Sūtra is the king in preaching the principle of perfect harmony and identity of all phenomena; the Wisdom Sūtra is the king in preaching the principle of voidness of all things; the Sūtra of the Great Assembly is the king in preaching to uphold the True Dharma; the Medicine Master Sūtra is the king in preaching the special vows of Medicine Master Buddha; the Sūtra of the Buddha of Infinite Life is the king in preaching the 48 vows of the Buddha of Infinite Life; and the Great Sun Buddha Sūtra is the king in preaching the finger signs (mudrā) and mantras; but none is the king of all sūtras preached during the Buddha’s lifetime. On the other hand the Lotus Sūtra is the great king who puts all the doctrines expounded in all the sūtras together and supervises them—such doctrines as absolute and relative reality, triple truth (truth of voidness, truth of temporariness and truth of the middle), finger signs (mudrā) and mantras, inactivity, 12 great vows of Medicine Master Buddha, and 48 vows of the Buddha of Infinite Life. I should say that he who understands this correctly knows the teaching.

Ken Hōbō-shō, A Clarificaton of Slandering the True Dharma, Writings of Nichiren Shōnin, Doctrine 3, Pages 120-121

Therefore we say that, although Buddhas, bodhisattvas, men, and gods appearing in various sūtras seem to have obtained Buddhahood through their respective sūtras, in reality they were truly enlightened because of the Lotus Sūtra. The four great vows of Śākyamuni and other Buddhas such as saving a countless number of people were fulfilled in this sūtra of the Lotus. In the second chapter, it is stated, “My (Buddha’s) wishes are all fully satisfied.”

Kaimoku-shō, Open Your Eyes to the Lotus Teaching, Writings of Nichiren Shōnin, Doctrine 2, Page 78-79

Expedient sūtras preached before the Lotus Sūtra are the same as non-Buddhist teachings, in which no one can be reborn in the Pure Land or attain Buddhahood. For instance, rivers which do not flow into the ocean cannot become one, and people and subjects who do not follow their great king cannot be united. No matter how hard we practice such teachings, there will not be any merit at all unless we reach the Lotus-Nirvana Sūtras; it will be the same as practicing the non-Buddhist teachings, in which Buddhahood is not attainable. They are the teachings nobody practices and no one can attain Buddhahood by practicing them in the Latter Age of Degeneration as well as during and after the lifetime of the Buddha.

Shugo Kokka-ron, Treatise on Protecting the Nation, Writings of Nichiren Shōnin, Doctrine 1, Page 22-23

The Lotus Sūtra preaches that living beings are endowed with three kinds of Buddha nature: shōin busshō, ryōin busshō as well as en’in busshō (virtuous deeds which enable one to develop “wisdom”). …

The Words and Phrases of the Lotus Sūtra, fascicle 10, preaches: “The shōin busshō is possessed by the Dharma-bodied Buddha, and it is innately possessed by all the people throughout the past, present and future lives. By nature they are endowed also with seeds of the en’in and ryōin busshō; these Buddha-natures are not acquired as a result of practicing Buddhism.”

Hasshū Imoku-shō, A Treatise on the Differences of the Lotus Sect from Eight Other Sects, Writings of Nichiren Shōnin,
Doctrine 2, Page 15-16

[I]t is stated in a letter signed by Former Governor of Musashi Province, Lord Hōjō Nobutoki, directing the Province of Sado on the seventh of the twelfth month in the tenth year of the Bun’ei Period (1273):

“There is a report that Nichiren, a priest exiled to Sado Province, and his disciples are engaging in corruption. His actions are inexcusable. From this point forward, those who follow Nichiren will be punished severely. Report the names of those who disobey this order. This is by the order of Lord Hōjō Nobutoki. 7th day of the 12th month in the 10th year of Bun’ei…”

The accusation in the letter of “engaging in corruption” is equivalent to the non-Buddhists who slandered the Buddha as a corrupt man. Moreover, the Buddha encountered the nine great difficulties such as the murder of Śākya Clan members by King Virūḍhaka, enduring begging without receiving alms and cold winds without proper clothes. I encountered persecutions in which my disciples were killed. I ate snow to stay alive, and I had no clothes to protect myself from cold winds. Do these difficulties exceed those endured by the Buddha? Perhaps T’ien-t’ai and Dengyō had not endured difficulties such as these. You should know that by adding myself to Śākyamuni Buddha, T’ien-t’ai, and Dengyō, there are now four practicers of the Lotus Sūtra, one of whom is in the Latter Age of Degeneration. How happy I am that I correspond with the Buddha’s prediction, “Needless to say, more people will do so (hate the Lotus Sūtra) after my extinction.” However, it is pitiful that people in Japan are falling into the Hell of Incessant Suffering by slandering me. The details are too complicated so I will stop here before this letter becomes too involved. Please consider the issue carefully.

Hokke Gyōja Chinan-ji, Difficulty of the Practicer of the Lotus Sūtra, Writings of Nichiren Shōnin, Biography and Disciples, Volume 5, Pages 15