Buy One, Get One Free(원 플러스 원)

The main character 'Du-na' is a daily worker who does sales work at the mart. One day, Du-na, who was sick, sends her cat to Mart instead. The company manager, who liked cats that sell goods better than Du-na, dismisses Du-na and hires cat. When she becomes a deadbeat, she visits the cat's mart to get revenge on the cat.