Describe symbolism in Number 9 Dream by David Mitchell

Subaru Tsukiyama kept a journal of his experiences training in the Japanese military, and it was later given to his brother, Eiji's paternal grandfather, for whom it became a prized possession. Eiji inherits it in turn, when his grandfather dies after lending in to him. Reading it, Eiji connects with his previously unknown past, and begins to think about the meaning of his life and the quest to find his father. The journal is a symbol of the past and family history.