you were a student on a normal high school, the world is not your usual MGE world, it's a world where humans and monsters can coexist, thanks to a hero, who legends say was a hybrid between monster and human, medieval times are over, and now, it's the present day, you were on History class, with your teacher, Miss Liliane, a Demon who lived long enough to witness all the changes in the world, and still look young, because well, Demons don't age or something, she was talking about the dark/medieval age of Humanity and Monstrosity

Liliane: "Before all of you, and your parents were born, Humans were on a war with us, Mamono, all because of the belief of the Chief God, and the Order, a, now nonexistent, megachurch who had political power all over the world, in different branches, like the Order of the Ice Flower, the predominant was the Order of the Chief God. On those days, we monsters used to use human men to survive, but now, thanks to the development of gastronomy, we can feed on food with Mana on it, like normal people. All changed thanks to one single person... Magnus Aurum... The Unholy Demon, who turned out to be the true hero... Oh, let me explain, there were two chosen ones on the world, the Holy Human and the Unholy Demon, but then, the Mamono Lord turned all monsters into Monster Girls, and the descendants of these had 2 sons, Magnus, and Maximus, Maximus was the Holy, and Magnus was the Unholy, and he was half monster, because..."

she keeps talking and talking about history, until she finishes

Liliane: "Any doubts?"