There is one toilet on the 1st basement floor, where various women visit day by day. A heart-broken office girl, a lonely sanitation worker, a high-school girl and so on... They happen to start communicating through the wall inside the toilet while using it as a bulletin board.
One day, before the beginning of spring, a woman leaves a note on the wall, which says "Cherry blossoms will bloom soon. Why don't we go to see them together?"
They meet up under a cherry tree. They identify each other by holding toilet rolls in their hands.