Starlight Academy is a large-scale learning institution where the students go about independent daily life within the school's isolated community. There, Yuko Maeda has recently started her first year in high school, expecting the peaceful days within the walls of the academy to continue. However, one night after encountering an otherworldly creature, Yuko finds herself with gaps in her memory, and questions about her true nature begin to arise. Dragged into a conflict greater than she can imagine, how will Yuko deal with her new circumstances?