Chiharu, a 22-year-old newcomer from the countryside, works at a prestigious downtown department store in Tokyo. Struggling to adapt to her new job, she grows fond of her kind and thoughtful senior colleague, Yuka. Two years older, Yuka can be strict at work but is gentle and caring in private, always looking out for Chiharu. One day, she suddenly invites Chiharu out for dinner. After drinking heavily, Chiharu becomes completely intoxicated and ends up at Yuka's apartment. However, the shocking twist awaits—Yuka is actually Bian.