Gao Wu: the Demon King Is Working in My Underworld

Ling Xuan, a powerful man of the generation, sacrificed himself to suppress the Demon Emperor and build the underworld. Three hundred years later, he was reborn as a useless high school student, only to find that the underworld he had built in his previous life had developed into a "financial institution" with complete procedures and skilled business. The biggest enemy back then is now the number one "debtor" in the underworld. And he himself became the only and legal heir of this "company". Thus, a wonderful (and invincible by the way) journey of debt recovery begins.