A priest of the True Word (Shingon) school in Japan.
He renounced secular life in childhood and became a disciple of Kobo (also known as Kukai), the founder of the True Word school.
In 824 he was granted the position of ajari (Skt acharya ), which qualifies one to transmit the secret doctrines of True Word.
After Kobo's death, he took full responsibility for Jingo-ji temple on Mount Takao.
Shinzei set out for China to further his studies, but his ship was wrecked by a storm and he returned to Jingo-ji.
In 856 he was appointed administrator of priests, the first True Word priest to receive that title.
He wrote The Life of the Supervisor of Priests Kukai.
He also collected Kobo's writings, including prose and poetry, and compiled The Collected Works of the Universally Illuminating Soul-Inspiring One.