Iron Widow By Xiran Jay Zhao

I have no faith in love. Love cannot save me. I choose vengeance.

The boys of Huaxia dream of pairing up with girls to pilot Chrysalises - giant transforming robots that battle aliens beyond the Great Wall. It doesn't matter that their female co-pilots are expected to serve as concubines and often die from the mental strain.

When 18-year-old Zetian offers herself up as a concubine-pilot, her plan is to assassinate the ace male pilot responsible for her sister's death. But after miraculously surviving her first battle, Zetian sets her sights on a mightier goal. The time has come to stop more girls from being sacrificed.