Following the story of Ran, who confronts a mysterious organization by participating in a no-rules deathmatch after discovering her missing younger sister Yuzuki is involved in a crime. With danger at every corner, Ran must trade in her boxing gloves for brass knuckles. Will she save her sister? (Source: Amazon) Adapted from the webtoon "Knuckle Girl" (너클걸) written by Jun Sang Young (전상영) and illustrated by You Sang Jin (유상진).