Tsubasa Tsubame is the next heir to the Tsubame Tenryu Ryouge, a martial arts school on the verge of collapse from financial hardship. Originally hired by Ukyou Sakinomiya to assassinate Yoichi Karasuma, she is a clumsy and shy girl who secretly dreams of a normal life as an ordinary high school student. She insisted on attending the same school as Yoichi under the guise of her mission, though her true intention was to experience the everyday life of a high school girl.

She developed feelings for Ryo Washizu after he became the first person to treat her normally, but was deeply hurt upon overhearing him say he hates martial arts. This inner conflict between her desired normality and her martial arts instincts surfaced during a school incident where she instinctively sliced a soccer ball hurtling toward her. An awkward silence followed until Yoichi broke the tension by greeting her openly.

When her subordinate, Angela Takatsukasa, grew impatient with her lack of assassination progress, she publicly ripped Tsubasa’s clothes off to trigger a transformation through extreme embarrassment. In this trance-like state, Tsubasa attacked Yoichi as ordered, but the fight was interrupted by Washizu. She broke from the trance and fled the scene in tears, later telling Angela she hated both her and martial arts—though she forgave her the next day.

Resolved to revive their school through honest means, Tsubasa and Angela opened a ramen shop together. Like Washizu’s recurring fantasies, Tsubasa experiences her own, referred to as the Tsubame Fantasy Channel in the manga and "Tsubame Vision" in anime adaptations. Her full name translates to "Sparrow’s Wings" or "Wings of a Sparrow" in Western name order. She has a younger sister named Enbi, who mastered all the Benten Ryuu Hidden Techniques by age eight.