Earphone Jack

Written Iyahon Jakku, Earphone Jack is a Mutant Quirk with a listed range of six meters, first appearing in chapter 11 and episode 8. Kyoka Jiro is its best known holder, and her mother, Mika Jiro, has it as well. Kyoka's Hero name is taken from the Quirk itself.

What it grants is a pair of long, controllable earlobes that function like the cables on a set of headphones. Kohei Horikoshi has said this may well be the earliest Quirk he ever devised, dating to before he had begun planning My Hero Academia at all.

The tips of Kyoka's earlobes are shaped into jacks, so she can plug them into a wide variety of objects. Once connected, she can push the vibration of her own heartbeat down the cable and into the object, wrecking it from within.

Listening is the other half of the ability. Plugged in, she catches faint noise through walls of considerable thickness, which makes her excellent on scouting duty. Her lobes stretch as far as six meters, and sound registers out to a radius of twelve. They are sturdy enough to punch through hard material such as concrete, and prehensile enough to work as spare hands, picking up small objects.

The vulnerabilities are the ones any limb has. The jacks can be injured, and they wear down under strain. At the First Term Final Exam, Kyoka pushed them hard enough in a short span that her ears began to bleed. A feedback problem exists too. If she is plugged into a surface when something extremely loud strikes it, an explosion for instance, the overload can put her out of the fight entirely. An opponent can also mislead her by flooding the area with competing noise to bury whatever she is trying to hear. Her Quirk Factor sits in her ears, so losing her left one to All For One in combat cut her down to a single working jack. A prosthetic replacement followed, of unconfirmed effectiveness.

Kyoka Jiro builds most of her Hero work around surveillance and support, reading enemy movement off the vibrations her jacks pick up. Offensively the lobes serve as whips that deliver a vibrating shock on contact. Her costume boots carry speakers she can plug into, firing a focused blast of amplified heartbeat in a chosen direction, though a competing noise of greater volume will cancel it out, Present Mic's Voice Quirk being the obvious example. The Quirk also does the mundane job its name implies, since she can plug into a device and listen to audio privately.

Her named moves run on the same principle. Counter-Balance uses the amps on her legs to raise sound waves that meet incoming attacks. Heartbeat Distortion routes her pulse through forearm amplifiers she slams into the ground, shattering it with the enhanced vibration. Heartbeat Surround detaches those wrist units, aims them at a target, and delivers a heartbeat that goes straight past conventional defenses to incapacitate. Legato is the scaled-up version, louder and stronger and pointed directly at the opponent. Heartbeat Wall repositions the amplifiers to raise a barrier of sound rather than a strike, first deployed against Izuku Midoriya.

Mika Jiro, Kyoka's mother, shares the Quirk. Whether she commands the full set of abilities her daughter demonstrates has never been confirmed.