Kaya Satozuka

The main character of the story, Kaya starts her position as private secretary to the Director at the beginning of the manga. She dresses very conservatively when at work, citing her professionalism, yet does so mainly because of her insecurity about her child-like looks. Due to her plainness, she is initially rejected by the Director for the job, yet she proves to be an invaluable worker and succeeds in gaining his acknowledgment. Despite discovering that the Director is a vampire, Kaya remains loyal to him and does everything in her power to protect his health and secret.

Over the course of the story, she starts developing feelings for the Director, and becomes torn between her responsibilities and personal life. Her blood is considered to be a special rarity, which is able to quench the Director's thirst with just a single drop. She eventually develops a sexual relationship with the director and leaves her official position as his secretary to work for a subsidiary company. Later on, she becomes the director's "midnight secretary", doing his office work at night in his mansion.