Recently, a unique example of the first juan of the 16 juan Foming jing with attached explanation and ritual directions was discovered in the Kongoji in Kawachi-Nagao City. Since it refers to the Jingang boruo jing zanshu 金剛般若経賛述 and the Jingang boruo yiji 金剛般若義記, it seems that it was written by the person well versed in the Jingang boruo jing (Vajracchedika Prajñaparamita sutra) 金剛般若経. Moreover, there are several portions which mention the number of the scrolls of this sutra and the total of the names of buddhas in it. Such descriptions are seldom seen in Chinese commentaries. There is a strong possibility that the method of the ceremony was written in Japan, because there are similarities to later documents about the ceremony of the Buddha names in Japan.
On the whole it seems to be the middle of composing the program of the ceremony for the Buddha names, so I think both the explanation portion and the method portion were written by the same person. Therefore the author seems to have been one familiar with the Jingang boruo jing who added the explanation and the method of the ceremony sometime between the 9th century and Kamakura-period (12th-14th century) in Japan.