[T]he underground bodhisattvas of chapter 15 have
special significance for Nichiren: “The countless bodhisattvas who had sprung up from underground were disciples of Lord Śākyamuni Buddha ever since the time He had first resolved to seek Buddhahood.” Although they had not visited Śākyamuni throughout his awakening under the bodhi tree and his expounding of the lesser sutras, since making their vow in the Lotus Sutra they are especially promised to appear in the mappō times, which Nichiren believed had already arrived.

Thus the underground bodhisattvas are greater for Nichiren than the familiar disciples, and even greater than the celebrated archetypal bodhisattvas such as Samantabhadra, Mañjuśrī, and Maitreya. “The numerous great bodhisattvas, who had been guided by the Original Buddha in the past, sprang out of the earth of the whole world, according to [chapter 15]. They looked incomparably superior to Bodhisattva Fugen (Samantabhadra) and Mañjuśrī, who had been regarded as ranking disciples. Even Bodhisattva Maitreya, successor to Śākyamuni Buddha, did not know who they were, not to speak of other bodhisattvas.”

Nichiren sees the underground bodhisattvas as the model for those who carry out the teaching of the enduring Śākyamuni in current conditions. And Nichiren himself personally identified with these underground bodhisattvas: “When these four great bodhisattvas, leaders of those who sprung up from underground, spread this sutra through aggressive means of propagation, they would appear as wise kings reproaching ignorant kings.” Practicing a persuasive means of propagation, they would be monks upholding and spreading the true dharma. In the final age of degenerate Dharma that Nichiren regarded as having arrived in Kamakura-period Japan, the imperative of proclaiming and propagating the Lotus Sutra teaching gained a new urgency. It was embodied for Nichiren by the enduring Śākyamuni and especially conveyed to the myriad beings by the underground bodhisattvas.