Kyoka Jiro, alias Earphone Jack, trains as a hero in U.A. High’s Class 1-A. Her Quirk, Earphone Jack, manifests as elongated earlobe jacks capable of detecting vibrations, emitting sound waves, and discharging electrical surges by converting her heartbeat. These versatile appendages stretch meters to pierce objects, gather audio intel, or strike foes. After the Final War, her left ear and jack are replaced by a prosthetic, though its operational limits are unspecified. Jiro presents a sardonic, pragmatic exterior, wielding dry humor to tease peers like Denki Kaminari. Beneath this lies fierce loyalty, showcased when shielding Momo Yaoyorozu from ridicule or devising tactical maneuvers during crises. Her sharp intellect, reflected in top-class academic standing, drives strategies like synergizing Kaminari’s Electrification with her Quirk during the U.S.J. Incident. Initially secretive about her musical passion due to doubts about its hero relevance, Jiro reconciles these identities after performing at the U.A. Festival as a bassist and vocalist. Embracing music as core to her persona, she modifies her hero gear with sound amplifiers, channeling melodies into enhanced vibrational assaults like Heartbeat Distortion. Growth arcs see her conquer insecurities over perceived inadequacy and fear of horror scenarios. In the Paranormal Liberation War, her defiance against All For One ignites rebellion among his captive Quirk spirits. Post-graduation, she rises to Pro Hero No. 30, mentors Eri, and balances heroics with a music career. Relationships shift from guarded to deeply collaborative. She forges a steadfast bond with Momo, bolstering her confidence, while maintaining a playful, mission-driven rapport with Kaminari. Their teamwork underscores her evolving trust in allies. Her costume progresses from a leather jacket and audio-equipped boots to armored sleeves, face paint, and later, a sleeveless jacket paired with her prosthetic ear—each iteration blending rock aesthetics with combat utility. Eight years post-Final War, her design retains this fusion of artistry and function.