What is the importance of Reiko's imaginary kingdom in the novel, The Ten Loves of Nishino?

The kingdom that Reiko imagines in The Kingdom at Summer's End serves as a symbol of the future. Unlike Nishino, Reiko sees the future as a magical realm. She is not afraid of the future, because she believes that it beholds a better life and reality than the present. At one point she promises to show Nishino the kingdom, as if she is promising to show him a version of the future that he does not have to fear.