Center-sensei's Center Exam

Center-sensei hosts an exam in which the girls must go into the world of the arcade robot shooter game, Border Break, where they can win a large amount of medals. Saturn, the only one who has to go on foot, is made into a decoy for the enemy, while Dreamcast struggles with her controls, leaving Mega Drive to take on most of the enemies. But as they're about to reach the core, suddenly, an Egg-shaped menace rears its ugly head! But wait! What is this blue streak that's speeding by?