It is believed that in the early Heian period, thirty-seven-year-old Kukai (Kobo Daishi or Great Priest Kobo) entered the temple to live there, and designated it as the first temple of the Shingon sect.
平安時代初期には37歳の空海（弘法大師）が入山し、真言宗最初の道場と定めたとされる。