Miu Serizawa holds the position of class vice-president alongside Yuuji Kagura. She is in a relationship with class president Kōsuke Machida, though she prefers to describe their pairing as a fortunate circumstance for him rather than openly acknowledge it. Like Machida, she is quite talkative, though Yuuji typically ignores them both and often fails to remember her.

She displays sadistic tendencies and a short temper, frequently using any pretext to strike Machida physically—including hitting him between the legs—as punishment for his perverted actions. She also threatens others with violence for sarcastic comments. Despite this aggressive behavior, she remains one of the more rational members of her class.

On one occasion, she reveals to Yuuji that Kazuki Arisaka once had a crush on a former teaching intern at their school, causing considerable tension. Miu has black hair tied in a ponytail with a ribbon, brown eyes, and is a teenager.