Madoka Owada is a 17-year-old student in Class 2-B at Gokurakuin Girls' High School. She stands 162 cm tall and weighs 52 kg, with physical measurements of 110-60-88 cm. Her large bust size, a G-cup, earned her the nickname "Boob Monster" from her classmate Aya Akabane. Madoka has black hair styled in pigtails, brown eyes, and wears glasses.

Her quiet and secretive exterior contrasts sharply with her highly perverted imagination. She openly identifies as lesbian and frequently expresses her sexuality through intense fantasies about romantic or sexual relationships between female students, especially involving Aya Akabane. These vivid fantasies consistently trigger severe, dramatic nosebleeds. Madoka demonstrates tolerance towards Aya's teasing about her physique, passively accepting the nickname and related comments.