In a society teeming with superhumans, Kouichi Haimawari dreams of heroism despite his modest 'sliding' Quirk that keeps him grounded. Embracing small acts of kindness, his ordinary routine shifts when saved by the underground hero Knuckleduster. Recruited to combat the dangerous drug 'Trigger,' Kouichi transforms into a Vigilante, straddling the line between law and justice in Vigilante: My Hero Academia Illegals, a prelude to the main tale.