Mai-HiME

A new high school student, Yuuichi Tate, discovers his school is frequently attacked by creatures known as "Orphans." The school has established a female task force called "HiMEs," who wield elemental powers to combat them. Each HiME has a "Key"—a person who can form a "Child," a combat unit, when paired with them. Yuuichi is revealed to be the Key for two rival HiMEs, setting off a series of conflicts.