Aki Katsuyama works as a gynecologist at Kiyosato Hospital. Renowned for her beauty, she also carries a reputation as a man hater. Approaching 30, she remains a virgin. Her professional duties place her near Shuuji, though she starts with no link to his planned revenge against Vice Director Takao.

Her path collides with the central conflict after noticing unusual, depressed behavior in her colleague, Haruna. Worried about Haruna's state, Aki agrees to share a meal during a night shift break, hoping to discover the source of her distress. This choice unintentionally leads Aki into a trap where Haruna ambushes her. Consequently, Aki finds herself forcibly recruited into Shuuji's scheme against Takao.