In the brutal hallways of a Korean high school, academic excellence is the only currency that matters—until violence becomes the only language the bullies understand. Weak Hero follows the unlikely story of Yeon Si-eun, a top-ranked student who appears fragile and unassuming, yet possesses an extraordinary strategic mind and fierce determination. When he becomes the target of the school's ruthless delinquents, Si-eun refuses to be a victim, instead using his intellect and unconventional fighting style to turn the tables on his tormentors. Alongside his loyal friends, including the hot-headed but kind-hearted Ahn Soo-ho, Si-eun navigates a world where power is measured by physical strength and alliances shift like sand. This gripping action-drama blends intense fight choreography with psychological depth, exploring themes of justice, friendship, and survival against overwhelming odds. As Si-eun rises through the school's violent hierarchy, he discovers that the weakest person can become the most dangerous opponent when backed into a corner.