Big robots,

fighting off aliens,

piloted by pairs of young men and women (mostly boys and girls), with the men draining the life force from the women (often killing them in the process).

Wu Zetian, eventually becoming the Iron Widow, is sold to the army by her family to become a concubine-pilot. She has a plan to avenge her sister, burn the system to the ground and build it back up again.

Dayummmmmm this was good.