This story looks like Hundred but it is not related to it by anything but parts of the plot. There are no characters from the anime. I wrote it here because it was the most similar topic to my story. Here's the summary:Humanity is attacked by mysterious alien race the only weapon that can defeat the monsters easily is the ONE. Can the wielders of this weapon save the world?

Liddy Steinberg was a warrior but she was still a girl. Hayato was someone unwillingly dragged into the conflict of the world for the sake of his sister. When two opposites come together it creates a bond. A Strange Attraction.