Nichiren Daishonin wrote this letter at Minobu in 1277 to Ikegami Hyoe-no-sakan Munenaga, the younger of the two Ikegami brothers, expressing his joy at conversion of Munenaga's father, Saemon-no-tayu Yasumitsu. For many years, Yasumitsu had stubbornly opposed his sons' belief, attempting to divide the two by twice disowning the elder brother, Munenaka, and promising to make Munenaga his heir if he would forsake the Daishonin's teaching. Throughout this ordeal, Munenaka stoutly refused to abandon his faith, but Munenaga wavered from time to time. However, thanks to the Daishonin's repeated letters of admonishment, he was able to resist the pressure of Yasumitsu's demands and eventually made a firm commitment in faith. Now that the two brothers had at last overcome their father's opposition and persuaded him to embrace the Lotus Sutra. Nichiren Daishonin warmly congratulated Munenaga in particular, praising his decision to remain true to his father and to his elder brother.

However, as the postscript indicates, this letter was intended not only for Munenaga but for all the Daishonin's followers. Its more general content begins with the passage, "According to the teachings of the true sutra, when the world enters the latter age and Buddhism falls into complete disorder, a great sage will appear in the world." This refers specifically to the Jinriki (twenty-first) chapter of the Lotus Sutra, in which Shakyamuni Buddha transfers the Lotus Sutra to Bodhisattva Jogyo, to be propagated in the Latter Day of the Law. Like the pine tree that withstands the frost, the Mystic Law, the heart of the Lotus Sutra, remains valid and flourishes even in the evil Latter Day when other Buddhist teachings fall into decline.

The last part of the Gosho warns against the erroneous teachings of the Shingon Sect. In the period spanning the late twelfth through early thirteenth centuries, over the course of a long and bloody struggle, warrior clans had succeeded in wrestling authority from the Imperial court. Nichiren Daishonin here attributes the collapse of the imperial government to reliance on Shingon, remarking that at two vital junctures, the court and its supporters sought the protection of esoteric Shingon prayer rituals, with disastrous results. When this letter was written, plans were in motion to employ the Shingon rituals yet again in an attempt to thwart the impending Mongol invasion. The Daishonin warns that so long as the people spurn the true teaching of the Lotus Sutra and place their trust in distorted interpretations of Buddhism, only suffering can result.