In the original story, Maudgalyāyana cannot assist his mother with his own magical powers; he can only do so by the power of the dharma. The fact that she is saved when he offers a meal to the monastic assembly reflects the widely held idea that the transfer of merit to the deceased is most efficacious when ritually mediated by monastics, especially those earnest in practice and pure in their vows. … Nichiren presents an alternative explanation, showing how he adapted traditional Buddhist stories to his Lotus exclusivism:

The Urabon service began with the Venerable Maudgalyāyana’s attempts to save his mother, Shōdai-nyo, who on account of her miserliness and greed had fallen for five hundred lifetimes into the realm of hungry ghosts. But he could not make her become a buddha. The reason was because he himself did not yet practice the Lotus Sūtra, and so he could not lead even his own mother to buddhahood. But at the eight-year assembly on Vulture Peak, he embraced the Lotus Sūtra, chanted Namu Myōhō-renge-kyō, and became the Buddha Tamālapattracandanagandha [Tamālapattra Sandalwood Fragrance]. At that time, his mother became a Buddha too.

You also asked about offerings for hungry ghosts. The third fascile of the Lotus Sūtra says, ‘It is as though someone coming from a country suffering from famine were suddenly to find a great king’s feast spread before him.’ … When you make offerings for hungry ghosts, you should recite this passage from the sūtra and also chant Namu Myōhō-renge-kyō.

Claims that one person’s religious attainment would simultaneously benefit that individual’s family members, sometimes for seven generations in each direction, was common in Nichiren’s time. They express a confidence, grounded in Mahāyāna notions of interconnection, that one’s own practice affects others across time, space, and the boundaries of life and death. Nichiren here assimilates such ideas to the practice of chanting the daimoku, the title of the Lotus Sūtra.

In developing his teachings about the daimoku of the Lotus Sūtra, Nichiren drew upon and adapted earlier traditions of Lotus interpretation. Chinese exegetes had often employed a technique known as “analytic division” (Ch. fenke) or parsing that purported to uncover categories of meaning implicit within a particular sūtra, and thus, to reveal the Buddha’s true intent. Zhiyi, for example, divided the Lotus Sūtra into two sections: the first fourteen of its twenty-eight chapters, he said, represent the “trace teaching” (Ch. jimen, J. shakumon), which presents Śākyamuni Buddha as a “trace” or manifestation, that is, a historical figure who lived and taught in this world, while the second fourteen chapters constitute the “origin teaching” (benmen, honmon), which presents Śākyamuni as the primordial buddha, awakened since the inconceivably remote past. The intent of the trace teaching, Zhiyi said, lies in opening the three vehicles to reveal the one vehicle, while the intent of the origin section is to reveal the Buddha’s original awakening in the distant past. Nichiren also regarded these as the two great revelations of the Lotus Sūtra. For him, the trace teaching revealed buddhahood as a potential inherent in all beings, while the origin teaching presented it as a reality fully manifested in the Buddha’s life and conduct. Nichiren saw the core of the trace and origin teachings as Chapters Two and Sixteen, respectively, and urged his followers to recite these chapters as part of their daily practice.

Chinese commentators … typically divided sūtras into three parts: an introductory section, the main exposition, and a “dissemination” section, urging that the sūtra be transmitted to the future. Zhiyi divided the Lotus Sūtra accordingly: Chapter One of the Lotus Sūtra represents “introduction”; Chapters Two through the first part of Seventeen represent the “main exposition”; and the latter part of Chapter Seventeen and the remaining chapters represent “dissemination.” Zhiyi further divided each of the sūtra’s two exegetical divisions, the trace and origin teachings, into these three parts. Nichiren expanded this threefold analysis in two directions. Zooming out, as it were, he applied it to the entirety of the Buddha’s teachings: all teachings that preceded the Lotus Sūtra are “introduction”; the threefold Lotus Sūtra is the “main exposition”; and the Nirvāṇa Sūtra, which Tendai tradition regards as a restatement of the Lotus Sūtra, represents “dissemination.” Zooming in, he identified all the teachings of all buddhas throughout space and time, including the trace teaching of Lotus Sūtra, as preparation, and the daimoku, Namu Myōhō-renge-kyō, the heart of the origin teaching, as the main exposition. Nichiren did not say explicitly what “dissemination” would mean in that case. His later disciples put forth various explanations, for example, that it referred to the spread of Namu Myōhō-renge-kyō in the mappō era.