At Sado, Nichiren began to make distinctions between the traditional Tendai manner of reading the Lotus Sūtra and his interpretation of the scripture. The traditional Tendai teaching divided the scripture into two parts: the first fourteen chapters were called shakumon (realm of trace) and were thought to reveal the unity of the teaching (one vehicle doctrine), and the second fourteen chapters were called homon, the true teaching.

Nichiren divided the Lotus Sūtra into three sections, which overlapped the traditional Tendai two-part division of the text. According to Nichiren, in Chapters Ten to Twenty-two, the third section, the practice of the bodhisattva was stressed. Nichiren considered Chapter Sixteen, “Revelation of the (Eternal) Life of the Tathāgata” the most important chapter of the text, since the eternity of the Buddha was shown to be clarified and understood through the continual, eternal practice of the bodhisattva, and this eternal life of the Tathāgata could be perceived through the practice of the bodhisattva. In this third section the bodhisattva was seen often as a martyr who must suffer for the sake of the truth. For instance, in Chapter Thirteen, “Exhortation to Hold Firm,” and Chapter Twenty, “The Bodhisattva Never-Despise,” it is stated that bodhisattvas will suffer and die in order to propagate the Lotus Sūtra.

Nichiren argued that Chih-i and Saichō understood the Lotus Sūtra only theoretically and hence only as a provisional teaching, but that he, Nichiren, understood the scripture factually in that he was living the text through his suffering and hardships as predicted in the text itself.