Blade of the Phantom Master

Long ago, there were royal inspectors in a country called Jyushin. They disguised themselves as shabby travelers and passed through towns, big and small. The duty of these inspectors was to find corrupt officials and punish them. But Jyushin has fallen. The world is corrupt, and no one answers the cry for help from the suffering people anymore. However, one royal inspector remains, roaming the lands... 

(Source: WEBTOON) 

 *Note: In 2017 the manga was rebooted as a webtoon manhwa with the original panels being recut and recolored to fit the format. The new release has 285 chapters (including chapter 0 and 11 side stories), serialized from 2018-01-19 to 2019-08-31.*