Humanity was under attack by an army of inter dimensional monsters.
Men were killed or enslaved in horrendous conditions and were used to give birth to monsters. A world in chaos ...
A few years of monster tyranny pass.
And another creature appears from the other dimension.
Giving humanity powers to fight against the monster army.
Fighting against the monster legions in their dazzling outfits.
Humanity is called these saviors, "Magical Girls".