Knights is a shonen manga tale about squire Mistletien, called 'Mist' for short. Taking place in a medieval world in which the church and her representatives are burning people en masse on suspicion of witchcraft, Mist and his organization are taking a stand against the church and the 'Saints' who are perpetuating the witch hunts. Mist is feared and hated by the village-folk because of his appearence, wearing a mask to disguise himself and going by the moniker 'The Black Knight.' He travels with Euphemia, a young girl who is as expert with mixing potions and poisons as Mist is with a sword. -Bakaupdates

BH007:
This Manga cannot be strictly classified as a historical manga because it's not actually set in a true historical era, but the political issues covered, which include Religion, Anti-Theocracy-ism, Racism etc allows it to be classified somewhat as a historical manga.
The manga does cover various somewhat mature "themes" but touches only on what is neccessary with almost nothing graphic or disturbing actually shown.