A legend holds that there were eight forefathers during the time in which Mikkyo occurred in India; this was conveyed to Kukai (Kobo Daishi) through China, and subsequently Kukai established the Shingon sect.
密教がインドで起こり、中国を経て、空海（弘法大師）に伝えられ、日本で独立した宗派として真言宗を開くまでに、八祖を経て伝えられたとする伝承がある。