A Certain Scientific Railgun Vol. 5 (manga)

Mikoto Misaka is left reeling from the revelation that Academy City's scientists have used the DNA she donated as a child, which was meant to be used for curing diseases, to create a veritable army of emotionless clones! And worse, these clones have only one purpose in life - to die over and over at the hands of the Accelerator, so that he may achieve ultimate power!