Yuzuki Hanyū is the homeroom teacher for Shōta Doi's class at Keimon West Private High School. She has black hair with brown highlights, green eyes, and wears glasses, standing at average height with measurements of 94 cm bust, 56 cm waist, and 85 cm hips. Her typical attire includes professional clothing such as sleeveless turtlenecks, long skirts, stockings, and heeled shoes.

Before the MK virus pandemic, she consistently supported Shōta Doi when classmates bullied him due to his cellular sclerosis. She detected his fever during a piano session in the music room and urged hospital treatment. Later, she informed his class of his diagnosis and impending cryosleep, showing sympathy when peers dismissed him. After Shōta's five-year cryosleep, she reunited with him at school, embracing him with visible relief. She initiated a romantic relationship with him, offering intimacy as a "reward" for overcoming his illness, leading to regular sexual encounters in her dormitory and the school music room.

She later experienced breast pain from their frequent interactions and requested Shōta's intervention as a "good luck charm." Simultaneously, she expressed emotional conflict about their relationship, questioning if he regretted their intimacy and crying while referring to him belonging to "everyone." External circumstances forced her departure from Keimon City, officially for family reasons. Transported to Tokyo, she relocated after a terrorist attack and was later revealed to be pregnant with Shōta's child, covertly hospitalized in a medical facility within a refugee district.

Her hobbies include playing piano, with a preference for classical music and a dislike for pigeons.