I think she has amnesia due to magical interference though. Like the fire didn't erase everyone's memories of her. The aunt also had some sort of appraisal power to tell if he was dangerous. I was already intrigued as to why someone wanted to make her not exist and who might be after her. So to me it's part of an interesting mystery in the story rather than the same tired trope. To each their own, I just want others to know that the amnesia is not just oops accident.

I’ve read all 20 ch so far and loved the beginning
But then
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Spoiler warning
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She gets amnesia! Just when he was about to meet her! ヽ(`Д´)ノ
I was expecting them to meet and start a cute story in a small village but really this cliche! Even if they went with the same story without the amnesia it would have been better! (╯°Д °)╯╧╧