On April 25, 1273, Nichiren wrote what he noted in his Covering Letter of the Kanjin Honzon-shō, Kanjin Honzon-shō Soejō, to be his most important work, The Object of Worship to View One’s Heart, or Kanjin Honzon-shō. The main writing’s full name is A Treatise Revealing the Spiritual Contemplation and the Most Venerable One for the First Time in the Fifth 500-year Period after the Death of Śākyamuni Buddha, Nyorai metsugo Go-gohyaku-sai shi kanjin Honzon-shō. The title shows it as clearly illustrating the Odaimoku and Focus of Devotion of the Original Gate of the Lotus Sūtra, and a “Letter that opens and reveals the Dharma.” It first lays out the Odaimoku of Namu Myōhō Renge Kyō as possessing the two laws of “the cause of practice and the effect of virtue” of Śākyamuni Buddha, the WorldHonored One, making it the correct Dharma for the Latter Age of the Dharma. Embracing and preserving faith and practice in the Odaimoku leads us to the salvation of Śākyamuni Buddha, the Master of the Teachings of Buddhism. Secondly, it illustrates that this world of Sahā [in which we live] is the Pure Land where the Original Buddha resides and shows the subject and features of the focus of devotion. Finally, it indicates clearly the correct teacher who propagates the Lotus Sūtra during the Latter Age of the Dharma as one of the bodhisattvas of the original teaching, honge no bosatsu, [specifically sent by the Tathāgata to lead all living beings to Buddhahood] who appear from underground in Chapter 15 of the Lotus Sūtra.

On July 8, based on the explanation provided in the Kanjin Honzon-sho, Nichiren Shōnin inscribed and revealed the first Mandala Gohonzon.