Who they were
Kukai (774–835) was born in Sanuki, on the island of Shikoku. In 804 he sailed to Tang China with an official embassy and studied esoteric Buddhism in Chang’an under the master Huiguo, returning in 806 with texts, mandalas and ritual implements.
What they did
He founded the Shingon school of esoteric Buddhism in Japan. From 816 he established the monastic center on Mount Koya, and in 823 he received the great Kyoto temple To-ji. He was also a renowned calligrapher and a prolific author.
Legacy
He was posthumously titled Kobo Daishi in 921. Later tradition credits him with countless works — even inventing the kana syllabary — but scholarship treats these attributions as legend. The Shikoku 88-temple pilgrimage retraces sites associated with him, and believers hold that he remains in eternal meditation on Mount Koya (a matter of tradition). He stands among the most influential figures in Japanese religious history.