Mahou Shoujo of the End

A high school student named Kogami Kii witnesses a bizarre event when a small girl attacks a teacher, causing her head to explode. Initially thinking it is a dream, he later discovers the horrifying reality when the same girl kills his classmates while repeating the word "magical." Kii and his childhood friend, Tsukune, observe as the victims' bodies return as a zombie-like group, also chanting "magical." Together with other survivors, they attempt to survive and uncover the cause of this strange phenomenon.