It's not so much that he didn't see his collage friend as a woman or she didn't see him as a man, it's that MC-kun is such a Japanese(beta) that he doesn't see anyone as a woman (see declining population).
... said nobody outside of Japan ever. Dissembling every time you open your mouth could only be considered a virtue by a socially shackled nation of habitual obfuscators.
It's incredibly easy to prove she has magic at least, if not from a different world. If we got a group of people who only spoke their own specific language, and she talked to them in their local language simultaneously, then you've proven that the universal translation magic exists. If you prove the universal translation magic exists, then the rest of her story becomes plausible. Science wins again.
@SotiCoto
People who are too straight forward exist in European countries too kiddo. I don't you're going to pick up many chicks if you start the conversation with "Do you want to fuck?".