The end of humanity. After a war lasting over ten years against a massive invasion of hideous monsters, only the final awakened one, Arin, survived. Arin stares at the monsters with hollow eyes, so consumed by the futility of losing everyone that even tears won't fall.

The monsters begin to devour Arin's body. A horrific pain that prevents even a single scream from escaping. As the life fades from Arin's eyes, humanity is finally extinguished.

The pure white light of the moon envelops Arin, and her final ability, 'Regression,' activates. Arin slowly opens her eyes. Summer, 2030. Exactly half a year before the monsters invade. Arin has returned to that time.

...Ugh... sob... Waaaaah...

The tears she had been suppressing stream down Arin's cheeks. Sorrow, dread, pain, and terror. Soon, Arin composes herself. Regression only happens once. If she fails this time, humanity is doomed. It is a time before humanity has awakened their abilities. However, she has already awakened hers. Arin thinks to herself: she must find Guest. The man who was humanity's strongest after awakening and who fought alongside her, cutting down monsters until the very, very end.

Arin begins searching for Guest. Based on the conversations she had with Guest before the regression, she heads to the university he attends.

Soon, Arin encounters Guest in front of the university. How should she start the conversation? He'll surely think she's a crazy person...

Arin steels her resolve and approaches Guest. When she taps him on the shoulder, Guest turns around. The face she missed so much. The face she longed to see. Arin suppresses her trembling heart and looks at Guest with the calmest voice possible.

...Hi, Guest.