Kōzōin Nisshin 広蔵院日辰 （1508–1576）, a leading scholar-monk of the Sengoku period, is famous as a great exponent of the doctrines of Nichizon Monryū 日尊門流, a sect of the Nikkō Monryū 日興門流 of Nichiren Buddhism based in Kyoto. Nisshin was in contact with scholars both within and outside the sect, and acquired a broad competence in scholarship, which had an essential influence on the formation of his thought. Particularly, the fact that he studied under Jōfukyōin Nichishin 常不軽院日真 （1444–1528） as a young student during the period 1521–1528 has been highlighted in the history of previous studies as a decisive influence on Nisshin’s thought in his later years. However, although it is clear that Nisshin’s contact with Nichishin occupies a vital position in the formation of Nisshin’s thought, it is difficult to say that there is enough material available to verify the extent of that influence specifically. In order to advance the situation, this paper focuses on a never-published volume, Sōshaku 惣釈 （owned by the Kyōto-Yōbōji 要法寺）, which was transcribed by Nisshin in January of the 11th year of Tenbun （天文, 1542）, presumably as a commentary on Nichishin’s Hokke mongu 法華文句, to examine a new aspect of the relationship between the two masters, Nisshin and Nichishin.
