In Maihama City, high school student Kyou Sogoru enjoys a typical routine of swimming, gaming, and hanging out with friends until the enigmatic Shizuno Misaki invites him to plunge into the school pool, catapulting him into a war-torn realm. Here, humans deploy Zegas—gigantic robots—to battle the alien Gards-Orm threat. Amidst joining the rebel group Cerebrum and engaging in intense combat alongside other Zega pilots, Kyou navigates a world filled with strife and sacrifice, prompting profound reflections on reality and purpose.