Twenty years ago, the combining robot Dandivine defeated the mysterious alien invaders known as the Aposdoll, bringing lasting peace to the world. In the aftermath, the toy manufacturer Kasuga built its entire business around Dandivine merchandise, but that dependence eventually led the company into severe financial decline. Kasuga's president, Genjuro Shijima, desperately prays for Dandivine's return, even if it means breaking the peace. His wish is granted when the Aposdoll suddenly reappear in Tokyo, throwing a generation that has known only peace into panic.

High school student Gekiha Shijima is drawn into the crisis when his uncle, Yusaku Kuroiwa—the original main pilot of Dandivine—recruits him to take the legendary machine's controls. Gekiha, alongside his cousin Kirei Shijima and classmate Akane Kuzumi, must pilot Dandivine and a team of other mecha such as Slash Unicorn, Dande Ace, Magna Titan, and Blaze Garuda to repel the renewed invasion. The story follows Gekiha's struggle to master the robot and uncover why the Aposdoll have returned after two decades, while Kasuga fights to reclaim its former dominance in the toy industry.