From MangaHelpers:
In a world where the situation is rapidly worsening, an unusual all-girls high school is taking in first-year girls who have been orphaned. However, when they show up to the welcome ceremony, they find out that the situation is much different than they might have thought. The school is designed as an experimental ground to turn children with no relatives into weapons. Before they entered the school, they were given an injection that would allow them to manifest powerful aspects of animals. After watching her best friend get killed at the welcome ceremony, Tachibana Karin struggles to survive the chaotic, violent entrance to life at her new school.