Hizashi's Quirk allows him to increase the volume of his voice, giving him the ability to create loud high-pitched sounds.
The sound from Hizashi's Quirk is strong enough to cause people's ears to bleed and drown out the effects of two other sound-based Quirks. In the anime, whatever words he shouts appear in the sound wave as it travels in English.
The only known weakness of this Quirk is that the sounds emanated from this Quirk do not travel well underground, making this Quirk ineffective against anything moving through it.
- Human voice - Wikipedia article about the specific sound source Hizashi's Quirk is based after.
- Sonic weapon - Wikipedia article about sound being used as weaponry.