Mao Hamasaki, an intelligent career woman working as a female manager, is the oldest employee in her department and constantly troubled by the presence of a middle-aged male coworker known as a "window seat employee"—someone kept around despite being effectively sidelined. Although the company encourages him to take early retirement, he ignores the suggestion and refuses to leave. One day, he suddenly fails to show up for work without notice, prompting Mao to visit his apartment. There, she uncovers glimpses of his past life and finds herself drawn into an increasingly intimate relationship with him.