@adfjs With a decent learning tool, like a flashcard app, hiragana and katakana aren't that bad. I memorized those in a few hours back in college, and only needed the occasional refresher to remember them for 6 semesters of Japanese.
As for the kanji, it looked like she was looking up the meaning for a few of them, so he probably just meant that she had already moved onto learning some basic kanji and words.
He does describe her as a genius at some point, so she probably is abnormal, but memorizing under 100 simple characters in 2 hours isn't impossible.
Also translator... you didn't need to translate her learning Japanese. It ruins immersion if she is supposed to be looking at Japanese and the letters blatantly aren't.
I'm all for trash isekai with shitty plot but
author should've at least tried to make some sense. I knew full well this was gonna be a shit manga but atlest stay in the same dimension and this is coming from a trash isekai manga connessiour.