Youko is a classmate of Asahi and the daughter of a human and a vampire. Though she has long canine teeth, many other typical vampyric characteristics are downplayed, such as only getting tanned in sunlight or feeling guilty when entering a room uninvited. She has a Kansai accent, but speaks in honorifics so as not to expose her teeth. While initially coming across as haughty, her true personality is bubbly and absent minded. Her dream is to become a cool beauty, but has yet to accomplish this goal. Though initially friendly with Asahi, she develops romantic feelings for him, but keeps them to herself because she believes Asahi to like Aizawa. She is also often hungry, due to not being able to eat lunch for fear of revealing her teeth.