Stranger Into Familiar.

Two Teenage brothers with extraordinary fighting abilities. live in japan after coming from America. For reasons only they will tell you. They come across a ghoul man in the street on their way home. To a surprise two girls around the same age jumped in to save them. They had the boy come with them. To another surprise they where taking to all girl monster and evil hunting unit of the Japanese military. Call the monster Suppression Unit, made up of all girls that are themselves monsters. They would be the first and only boys to be aloud to join.