The novel follows Nana, a stray cat who is adopted by a kind young man named Satoru. They live happily together and share a strong bond.
One day, Satoru takes Nana on a journey across Japan to visit some of his old friends, claiming he is looking for a new home for the cat. During the trip, Nana gradually learns about Satoru’s past and the deep relationships he has with the people they meet.
It is slowly revealed that Satoru is seriously ill and is preparing for the end of his life. The story is a touching exploration of love, friendship, loyalty, and acceptance of death, told through the gentle perspective of a cat.