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Frank was suddenly visited by special souls, the souls of the visitors were of nobody else than Veronica and Ervas, powerful Primordial Children that lived all the way into the other side of the Universe.
These beings had already tried to contact Frank before through his parents, which they decided to aid in growing stronger and develop their new divine powers contained within their bodies, while their souls themselves were also nourished by them, and were even given fragments of their souls, granting each one of Frank's parents with their divine protections.
The divine protections of such strong beings had made them even stronger than they would had been originally, so Frank's parents were nothing but overpowered at this point.
Check "The Protagnist's Sister Is Actually the Strongest"!