Magical Girl Nanoha EXCEED SGUN

Thirty years ago, unknown aggressive alien creatures suddenly appeared, and the world was once on the brink of destruction. Humanity has been fighting for living space against these creatures, known as the Invasive Species. Although human safety is barely secured for now, the world could end at any moment. People, while fearing death and destruction, can only turn a blind eye to dangers and disasters, living their daily lives numbly. In such a world, the United Nations' Dangerous Organism Investigation Agency, EXCEEDS, has begun operations to counter the crises and disasters brought by the Invasive Species. The story begins on the remote island nation of Mizuho in the Far East. A hunter girl named Kushina Shiina, who lives on a remote island and makes a living by exterminating Invasive Species. Her only wish is to live peacefully with her only family member, her younger sister Setsuna. However, what is the incident that befalls Shiina?