Nittatsu expelled the Kenshokai and was the first High Priest to publicly criticize the Soka Gakkai for allegedly deviating from the traditionalist doctrines of Nichiren Shoshu.
He later threatened its senior leaders to remove the Dai Gohonzon from their funded building, the Shohondo, later demolished by his successor Nikken Abe.
Nittatsu Hosoi was born on 15 April 1902, in the Kyobashi neighborhood of Chuo, Tokyo, Japan and entered the Nichiren Shoshu priesthood in 1910 at eight years of age, training under 57th High Priest Nissho Shonin.
On 22 June 1979 at 5:00 pm, he died aged 77 of chronic heart disease at the Fujinomiya City General Hospital and was succeeded by Nikken Abe.
Nittatsu Shonin's transcription of the Dai Gohonzon image is notable for its clear print calligraphy and was issued on 1 January 1966 for woodblock dissemination.
He was also instrumental in the lawsuit brought by the Kenshokai group, led by Shoei Asai, who accused Soka Gakkai senior leaders of allegedly forcing Nittatsu Shonin to publicly declare the Shohondo building as the permanent sanctuary of the Dai Gohonzon as petitioned by Soka Gakkai President Daisaku Ikeda despite the Emperor Showa's not having made the Gojukai Buddhist conversion vow, which Kenshokai considered an absolute prerequisite for such a declaration.
As high priest, Nittatsu Shonin affirmed the confiscation of the seven wooden Gohonzons reproduced by the Soka Gakkai, resulting in a public apology on 8 November 1978 by Soka Gakkai president Daisaku Ikeda via Vice President Takehisa Tsuji, who published the following: "The Head Temple Taisekiji is the fundamental place for Buddhist practice.
Receiving strict guidance from the High Priest (Nittatsu Shonin), the Gohonzons that were carelessly engraved and reproduced were placed in the Hoanden (building)."
)After his death, among Nichiren Shoshu believers Nittatsu was remembered as the "smiling High Priest" for his pleasant demeanor in photos.