To defend against Nightfly O'Notes, invaders from another world, mankind has organized the five-man fighting team "Scar-red Rider XechS." However, one of the Riders, Yosuke, is saddled with a serious problem.

When Akira, the new instructor-in-charge, assumes her post, the Scar-red Riders' leader, Takt, finds himself unable to trust her. Friction arises between Takt and Yosuke. During all the discord, there is an enemy attack.

After being hurt in battle, Hiro's physical injuries heal, but as he grows more distant from the group, it becomes obvious that some mental wounds still remain. Akira tries to get the Riders to focus on their teamwork.