Tsubasa Hanekawa is Koyomi Araragi's classmate and class representative at Naoetsu Private High School. Renowned as a model student with top grades and a kind, approachable manner, this image conceals deep turmoil. Her family history is unstable: her biological mother became pregnant at seventeen, had multiple partners, and committed suicide shortly after her birth. A workaholic stepfather raised her initially but died from overwork. She now lives with a stepmother and another stepfather, both non-biological, enduring emotional neglect and occasional physical abuse while sleeping in the hallway. This fosters profound disconnection from her identity.

Externally soft-spoken and intellectually humble—often deflecting praise with "I don’t know everything, I just know what I know"—Hanekawa represses trauma, envy, anger, and stress as "impure" emotions. This suppression spawns supernatural aberrations. The first, Black Hanekawa, emerges violently during Golden Week, embodying accumulated stress. Later, the Hysteria Tiger manifests separately from her envy and resentment, specifically triggered by witnessing her guardians attempt reconciliation without her.

Her bond with Koyomi Araragi proves critical. They meet when wind exposes her underwear, breaking the ice; she initiates friendship by adding her number to his phone. She later shares vampire rumors, indirectly causing his transformation. Throughout his ordeal, she delivers supplies, strategizes, and witnesses his battles—sustaining life-threatening injuries healed by his vampiric blood. This infusion leaves supernatural traces, potentially influencing later aberrations. Romantic feelings for Koyomi develop, compounding her emotional burden when he dates Hitagi Senjougahara; this unrequited love generates stress rivaling her lifetime of familial trauma.

Physically, she evolves from braided hair and glasses to short hair and contacts after resolving the "Tsubasa Cat" arc, rejecting her suppressed self. Post-"Tsubasa Tiger," assimilating the Hysteria Tiger, her hair gains silvery-white tiger-like stripes she routinely dyes black. Accepting her "impure" emotions marks a turning point: she abandons perfectionism, embraces anger and envy, confesses to Koyomi anticipating rejection, and confronts injustices directly—like challenging Ougi Oshino.

After graduation, she travels globally, inspired by Meme Oshino. She aids refugees, removes landmines, and digs wells with NGOs, earning the moniker "Japanese Joan of Arc." Shifting to conflict mediation, she employs extreme measures to erase borders, becoming internationally wanted.