弘法大師 - Kobou Daishi
I have tried to search for information on this monk and I believe he was originally from Shikoku Island and was called Kūkai. He died on Mt. Kōya on April 23, 835 (by today's calendar), at the age of 62. In 921 an imperial order gave him the posthumous name of Kōbō Daishi. See here for more information on the person I believe to be him.