Brigadoon: Marin to Melan (2000)

In the year 1969, strange things are happening on Earth: a strange formation known as Brigadoon has appeared in the sky. In addition mysterious alien machines called Monomakia descend from this formation to hunt down Marin Asagi... a normal junior high school girl who had been adopted by an elderly couple. Luckily, Marin discovers a strange blue ampoule in a shrine, which summons an alien protector: a sword-carrying, gun-slinging warrior named Melan Blue. Together, Marin and Melan must save the Earth and find out the purpose of these attacks, and at the same time deal with family crises, prejudice, police brutality, and furthermore come to an understanding in their relationship.