Ruth is so preoccupied by Nao’s diary that she failed to register how much time has passed since Nao wrote it. This is evidence of Nao’s point that time is like a “slippery fish”—it can easily slip away from people without them realizing it. Ruth feels especially annoyed at her forgetfulness since she is already sensitive about her memory, and she sees any memory lapses as potential symptoms of Alzheimer’s. She is terrified that she will get Alzheimer’s, just like her mother did.