What specific devotee's history is highlighted as a primary focus in the introduction to Chapter 51?

The introduction to Chapter 51 specifically highlights the story of Kakasaheb as a main narrative to be presented. The author announces their intention to narrate the "marvelous account of how Kakasaheb was established in Shirdi." According to the details provided in Chapter 51, this account will delve into the entire history of his bond from past lives, referred to as 'rinanubandh,' with Shirdi and his firm relationship with Sai. The text notes that while many of Kakasaheb's stories were known, the particular story of how he first arrived in Shirdi was not common knowledge, making its inclusion significant.