Story
The OVA focuses mostly on the girls of St Ignacio's School for girls than the mecha itself. There are two clubs to join: The Debutante Club (華麗部 Kareibu, "Glamour Club"), where admission is said to lead to ultimate success; or The Etiquette Club (礼法部 Reihōbu, "Manners Club"), which is said to teach the values of common courtesy in the world.

Three freshmen join the Etiquette club rather than the popular Debutante Club and soon discover its founding members are part of a secret task force called Exters (ExStars in the dubbed version). Fan service is a predominated feature in the transformation sequence. The battles are not only for school hierarchy, but to save the world

Source: Wikipedia