Kim Sang-an is a cold-blooded loan shark.
When his younger sister, a schoolteacher, takes her own life after relentless bullying from her students, he becomes the homeroom teacher of those very students to collect the price of her life.
A merciless loan shark who will collect his debts even if it means descending into hell and a class of devil-like students...
A vicious, twisted teacher-student relationship.
