It describes that Fudo Myoo lives in the disciplinant's mind (Fudo Myoo is indeed a disciplinant) because the ways of the living things' minds aren't the same (the way of reaching enlightenment is different individually) so that Fudo Myoo makes their wishes come true by changing its figure in accordance with each person).
衆生の心の有り方は一様でない（悟りに到る道も個々によって異なる）ので心の中に住み（修行者自身が不動明王である）、各々に合わせて姿を変え願いを叶えるという内容が説かれている。