It's been 10 years since the Precure was last seen. "There all dead!" People and citizens would say. Some still believe their still here, but had just retired.
The Great Pretty Cure War had a huge impact. Cure Ruler, Blinded by power, Was sealed in the Oblivion Realm. The Precure used more power than expected to seal her away, but in return, they will sleep where time doesn't exist until someone comes in contact with them.
Seiyo Academy, studying about the Great War, lays the Guardians