Lee Haejoo isn't really given a choice when she's told that she has to become a debt collector or pay 960,000 dollars up front. She reluctantly agrees to work off her debt to Hoya, the head collector and founder of the Infinite Debt Agency. There are other people at the agency to pay off their debts too, but Haejoo is given the most strenuous jobs simply because her boss likes to make her work. Haejoo doesn't agree with any of the Infinte Debt Agency's policies or beliefs, but she eventually starts to love every one of the members as her family. But when she starts to see one of the members as someone more than family...chaos breaks loose.