Angetsu Yakou

Hattori Hanzo, the fearsome ninja known as “Demon Hanzo,” had retired from active duty. Yet, at the Lord's command, he was appointed to the secret position of “Undercover Fire and Theft Investigator.” Accompanied by the enigmatic girl Sei and the swordsman “Asaemon the Executioner,” who swore absolute loyalty to Sei, he set out to fulfill his mission, but...

(Source: Mag Garden, translated)