With her husband working away from home and her son accompanying him, Rin is enjoying the feeling of being single and living alone. One day, she finds out that Takuto, the son of a mom friend, is a part-time co-worker. Rin, who is frustrated by her sexless marriage, is intrigued by his muscular body and sneaks out for a drink alone... Since then, the two have been enjoying an affair limited to part-time workers, and they have been drowning in pleasure, repeating thrilling and exciting infidelity wherever they are during the workday. And every time she punches out, her body naturally starts to ache...