Sachiko, who moved in next door to Shuhei, who lives alone, wants to have children but has always been shy. Recently, her husband has been uncooperative about trying to have a child, and she is becoming increasingly anxious about child-rearing. One day, Shuhei confides in her worries, and Sachiko suggests that she practice child-rearing, and she offers to be the practice subject... Sachiko takes Shuhei seriously, treating him like a child, but there is no way Shuhei can control his reason with her large breasts in front of him... And so begins a secret rendezvous between the married woman and the young man, under the guise of child-rearing practice...