This chapter provides a short introduction to the book’s topic and the main questions motivating this study. I focus particularly on the multiple identities of Eison (1201-90), founder of the Shingon Ritsu movement (also known as the Saidaiji order); his grand-disciple Monkan (1278–1357); and the cult of the bodhisattva Mañjuśrī. I also briefly situate my interest in the diverse identities of these monks and the Mañjuśrī cult within broader issues in medieval Japanese society and religion.