Chisato lives with her husband and their son, Satoshi, in a family of three, but her husband is frequently away on business trips, leaving her mostly alone. One day, Chisato realizes she has washed all her underwear due to the continuous rainy weather and has no clean ones left. With no choice, she decides to go without panties. As she goes about her day, she feels an uncomfortable draft against her lower body, causing her to grow restless and fidgety without realizing it. Noticing his mother's unusual behavior, Satoshi comes up with a mischievous idea that will inevitably change their parent-child relationship forever.