This Playboy Is a Warlord

By day, he's a playboy who flirts with maids in public and refuses to pay his debts, becoming the laughingstock of the city; by night, he's a Robin Hood-like outlaw who robs the rich to help the poor and drives away barbarians! He disguises himself as a playboy for ten years just to survive under the Duke's watchful eye. When he finally sheds his disguise and leads his army to slaughter his enemies, the Duke watches helplessly as he rises to become a national hero. Meanwhile, the princess who despises the playboy but secretly loves the outlaw is filled with remorse upon learning the truth.