What is the primary theme and what metaphors are used to introduce it in Chapter 15 of the Shri Sai Satcharitra?

Chapter 15 introduces the theme of the loving relationship between the Guru and his devotees, and how persistent devotion can invoke divine grace. The chapter explains that it will describe how Sai grants his vision to his followers. As detailed in the text, two primary metaphors are used. First, the author compares the listeners to a vast ocean that accepts all rivers, both pure and muddy, signifying their receptive nature. Second, and more centrally, the relationship between Sai and his devotees is likened to a mother cat and her kittens. The kittens' loving persistence eventually causes the mother to forget her initial annoyance and provide milk, illustrating how devotees' sincere love can win the Guru's grace, as explained in Chapter 15.