Mahou Shoujo Lyrical Nanoha EXCEEDS: Gun Blaze Vengeance

Thirty years ago, a mysterious alien creature suddenly appeared and nearly wiped out humanity. Since then, strange creatures known as Invasion species continue to fight against humans for control of the world. A few human communities are still alive and fighting against them. To protect humanity, the United Nations created EXCEEDS, an organization that is responsible for human protection. 

The story follows the life of a young lady, Shiina Kuze, who lives on a remote island and spends her days hunting these Invasion creatures while protecting her little sister. However, an unexpected incident shattered their life completely. As dangerous secrets are brought to light, she must fight not just to protect her sister but also to protect the future of humanity.