The story takes place in an alternative timeline, where, in this universe, the human race is facing extinction. The only way to save humanity is by traveling back to the past and changing key events.
However, the villains introduced in the animation have discovered this plan and began traveling across different timelines, eliminating every alternative timeline one by one to prevent humanity from being saved.
Because of this, the featured character — a highly advanced Cyber-Human — is forced to return to the original timeline and remain there, since her own original timeline was completely destroyed.
From this point forward, the next episodes will further explore the consequences of the destroyed timelines, the nature of time travel, and the character’s struggle to exist in a reality that is no longer her own.