Insistence

To be more precise, the reason why Red had no memories back on the Zasfins' planet was simply due to his cultivation. As mentioned several times before, demon beasts only gained sentience at the Transition Realm. Red was nothing but a Stage Six Demon Beast back then, which was somewhere around the Soul Transformation Realm for a cultivator. Naturally, it made sense that he didn't have memories from the time he was in the Realm of Gods. 

Back in Kritalos Region, Rean received news that Red would be coming. Yet, he had heard nothing from the girls so far. 'Hmm... so Red got separated from Calina, Qia, and Zuo, huh?' After that, he shook his head. 'It's still too early to make guesses. Spreading the new information around the demon beasts' territory will take several weeks, if not months. And that's only because Placake has his own ways to make his voice reach the faraway lands of the demon beast territories.'