I heard there's a story about a ritualistic man in Chapter 12. What's the setup for that story?

Yes, Chapter 12 sets the stage for a delightful story about a man devoted to rituals. The chapter explains that by a stroke of good fortune, a "ritualistic, orthodox Agnihotri (keeper of the sacred fire) from the holy place of Nashik, with the surname 'Mule'," came to Shirdi. This visit was attributed to the strength of his past merits, as the text notes that without such merit, "no one can stay in Shirdi for even a moment." The narrative in this chapter suggests his original intention for the visit was different from what actually happened, but this coincidence led him to gain the benefit of being in Shirdi and seeing his own Guru.