Yuusha Ninteikan to Dorei Shoujo no Kimyou na Jikenbo

Humanity was once driven to the brink of extinction by the appearance of the "Demon Lord." It was the "Heroes" who defeated the Demon Lord and saved the world. In order to prevent the same thing from happening again, mankind decided to prepare for the resurrection of the Demon Lord by enacting the "Hero Recognition and Protection System," a system to keep several heroic braves on hand at all times. Time passed, and now... in an age when the threat of the Demon Lord has become a fairy tale, Miguel, the Kingdom's official for certifying heroes, and his partner, Dia, travel around the country looking for heroes. One day, Miguel hears a rumor of a "holy hero," a reincarnation of the hero who defeated the Demon Lord himself. When Miguel visits the mining city of Felicidad to investigate, he sees many miracles being performed by a girl they call the "Holy Hero"! Here is the start of a fantastical mystery about "miracles" and the "resurrection of heroes"! (Source: Lanove Bunko, translated)