Sachiko, a married woman who moved in next to Shuhei, lives alone and longs for children. However, due to her naturally shy personality, she struggles to communicate with her husband, who has recently become uncooperative in trying to conceive. Her anxiety about raising a child grows stronger each day. One day, Shuhei learns of her troubles and suggests they practice parenting together. Sachiko agrees to become his practice partner. Though she treats Shuhei like a child with serious dedication, her large breasts captivate him, and his self-control quickly crumbles. Soon, secret encounters under the guise of parenting practice begin between the young man and the married woman.