1. Maybe he turned back time which left him weak and vulnerable enough for something to "attach" itself to him.
2. Same thing, he turned back time with the demon king's power. This could have left open a "backdoor" of sorts that left him vulnerable to the black mana. Now he could be being used as a medium or catalyst to summon the demon king again. Resulting in the sword rejecting him.
3. Our FL probably didn't lose her memories because of her contract with the Phoenix. Since the Phoenix isn't affected this protection could have extended to her through the contract since it only became "thin" but not broken. In other words, the contract wasn't broken because it couldn't truly be "forgotten" as the being, the Pheonix, is unable to forget.
My theories
1. Maybe he turned back time which left him weak and vulnerable enough for something to "attach" itself to him.
2. Same thing, he turned back time with the demon king's power. This could have left open a "backdoor" of sorts that left him vulnerable to the black mana. Now he could be being used as a medium or catalyst to summon the demon king again. Resulting in the sword rejecting him.
3. Our FL probably didn't lose her memories because of her contract with the Phoenix. Since the Phoenix isn't affected this protection could have extended to her through the contract since it only became "thin" but not broken. In other words, the contract wasn't broken because it couldn't truly be "forgotten" as the being, the Pheonix, is unable to forget.
Thoughts? ヾ(❀╹◡╹)ﾉ~