Tejina-sempai anchors the narrative as a third-year high school student. She possesses striking silver hair, blue eyes, a notably large bust, and a distinctive skin-colored fang on her lip. Her standard outfit is a school uniform: a white dress shirt under a blue cardigan, a red bowtie, a navy blue pleated skirt, and black calf-length socks. For magic performances, she adds a black top hat and a black/red cape.

She burns with passionate enthusiasm for magic but suffers crippling stage fright. Alone, she performs tricks flawlessly; before an audience, intense anxiety triggers frequent mistakes, physical mishaps, partial nudity, visible flop sweat, trembling, and occasional vomiting. Despite repeated failures, she persists with resilient determination. Beyond magic, she displays athletic running ability and painting talent, though her academics are poor, requiring remedial tests to pass. She has a sweet tooth, enjoys baking cookies, and remains largely oblivious to the attention her appearance attracts, though she flushes with embarrassment when noticing leering. She fears balloons and proves highly suggestible to hypnosis.

Her magical knowledge is extensive, yet public demonstrations reliably collapse into slapstick mishaps—wardrobe malfunctions or accidental exposure—fueled solely by nervousness, not lack of skill. Her large bust occasionally obstructs trick execution, and sweaty hands during anxious episodes further hinder dexterity.

She recruits a first-year male student as her assistant, forming the series' core dynamic. She develops a possessive attachment, feeling jealousy when he interacts with girls like Madara from the Chemistry Club, sometimes shadowing their activities. Their interactions feature unintended suggestive comments, accidental lewd situations, and unacknowledged hints of mutual romantic feelings. Her older sister, a married teacher at the school and Magic Club advisor, frequently subjects her to cosplay outfits. She faces rivalry from street performer Saki, who challenges her for club leadership; this conflict resolves via a bust size comparison confirming her larger physique. Additional club members include Saki's brother Masashi, whom she comforts over sibling frustrations.

She inherited leadership of the school's Magic Club after all other members graduated, leaving her as the sole participant. This drives her aggressive recruitment efforts to prevent the club's dissolution. While her stage fright persists throughout the series, she gradually forms deeper bonds with club members. Her family background is minimally explored beyond her older sister's dual role as sibling and teacher. Spin-off media like *Isekai Senpai: Tejina Senpai wa Kono Sekai de mo Ponkotsu na Yō Desu* contain no concrete information expanding her background or development. The core narrative focuses on her persistent stage fright and club activities without substantial evolution of her personal circumstances or anxieties.