After his parents passed away in an accident during his school days, Yoon Seo-Ho borrowed money from a loan shark and got into a big debt. He is currently paying off his debt by helping with fraudulent gambling at an illegal casino run by the loan shark Jang Sa-Jang. A high school classmate who happened to see Seo-Ho like that proposes a plan to free Seo-Ho by beating Jang Sa-Jang at gambling...

(Source: Mr. Blue, translated)