What does Water from the Store represent?

The water from the store symbolizes the effects of one's setting and routines on one's personal essence. Like the sounds of the store, Keiko fills her body with food and water that she purchases from the shop. In this way, she considers herself as made up of the store, in that we are what we eat. When she quits the convenience store, she observes how after two weeks, none of the water from the convenience store remained in her body. This symbolizes how quitting her job made her lose the very essence of who she was.