Which specific devotee's arrival in Shirdi is set to be a focal point in Chapter 51, and what underlying spiritual concept is tied to his story?

Chapter 51 explicitly states that it will narrate the "marvelous account of how Kakasaheb was established in Shirdi." While his stories were widely known, the chapter notes that the circumstances of his initial arrival were not. The text introduces a key spiritual concept related to his connection with Sai Baba and Shirdi, explaining that it will detail the entire history of his 'rinanubandh,' which is described as a bond from past lives. As mentioned in Chapter 51, this concept suggests that his firm relationship with Sai was preordained due to karmic ties from previous existences, and the chapter promises to soothe the hearts of listeners with this and three other stories.