The story starts and ends with chapters set a few years later, when Mai learns that her grandmother has died and again visits the house in the country. What comes between is then an extended flashback. We see Mai gathering wild strawberries with her grandmother and making strawberry jam, walking on the hill at the back of the house, and doing household chores, including washing clothes by hand (or rather foot) since her grandmother doesn't have a working washing machine. Her grandmother claims to be a witch, and Mai decides to train towards the same ability. There is nothing unambiguously magical in the book; and the training largely consists of the household chores mentioned above, along with efforts of self control like getting up early. Grandmother instructs her in housework and at the same time dispenses wisdom about life.
I found this a difficult book to enjoy. Too much of the grandmother's wisdom seemed to me the kind of thing that people believe because it's comforting. And although I've often enjoyed stories that involve descriptions of simple activities like cooking, cleaning and gardening, the books that pleased me that way had a vividness that seemed lacking here. The simplicity and placid flow of Japanese prose is a particular strength of several of its better writers; here, it felt a bit lifeless, perhaps because there seemed too little complexity behind it. But the story does develop some complexity as it progresses and it left a better impression than my not very enthusiastic remarks above might suggest.
The bunko edition comes with a short story sequel, 渡りの一日 (Watari no ichinichi, "One day's crossing", 1996), following Mai and her friend Shouko over one day.