National Treasures & Important Cultural Properties
of National Institutes for Cultural Heritage, Japan

　　This is an esoteric Buddhist commentary by Kūkai (Kōbō Daishi; 774–835) that explains the title of the Diamond Sutra translated by Yijing (635–713). A kaidai (開題) is a formal interpretation of the title of a sutra and explication of its importance.
　　The Diamond Sutra itself has six Chinese translations of which the one by Kumārajīva (344–413) is most frequently used. However, the version that Kūkai used for his interpretation was that translated by the monk Yijing of the Tang dynasty. The Diamond Sutra attracted many devotees in Tang China, and stories of its miraculous power to benefit believers were compiled in the Miracles of the Diamond Sutra. The sutra also had a strong following in Japan. By the Nara period (710–794), a large number of copies was produced by the Scriptorium. During the Heian period (794–1185), belief in the powers and efficacy of this sutra grew even stronger. Stories from the Miracles of the Diamond Sutra, brought from China, were collected in Japanese compilations of Buddhist tales such as the Miraculous Stories of Karmic Retribution of Good and Evil in Japan, the Anthology of Oral Literature.
　　The Sanbō-in of the Daigoji Temple in Kyōto is believed to have originally owned this Kūkai’s Explication of the Diamond Sutra. At some point, however, it was removed from the temple and cut into sections. The extant sections of the manuscript total about 150 lines.
　　This segment in thirty-eight line was owned by the Takamatsu no Miya Family. A sixty-three-line segment in the collection of the Kyoto National Museum and other fragments are also known to exist. An eighty-six-line segment that was part of the first section of the original manuscript was destroyed by fire during the Great Kantō Earthquake of Taishō 12 (1923).
　　In the tenth month of Kōnin 4 (813), Fujiwara no Kadonomaro (755–818) completed 187 copies of the Diamond Sutra as an offering. Some years earlier, in Enryaku 23 (804), Kadonomaro had traveled to the continent as an ambassador to Tang China on the same boat as Kūkai. Their ship had met with a violent storm, and they drifted at sea for more than a month. At that time, Kadonomaro made a vow to 187 deities that he would make an offering of a copy of the Diamond Sutra to each one if the ship were spared. They eventually reached port safely, and Kadonomaro honored his promise by offering187 copies of the Diamond Sutra to the gods.
　　Kūkai wrote the dedicatory prayer for Kadonomaro, and it is thought that Kūkai’s Explication of the Diamond Sutra was authored at the same time. Since additions and corrections can be found throughout this manuscript, it is regarded a draft.