Shirasaki Megurin,a normal school girl,just like average girls she likes magical girls a lot when she was child and hope that she can become one.But that dream was crushed when her only family,her mother was killed by one of them.She was taken by a police officer who said had fight magical girls before.She trained very hard in order to pay back what they had done to her mother.She throw all that dreams she had before and now she has only one goal,to wipe out all magical girls.