Honestly, I can see how Kanji wouldn't have thought to ask her about seeing magic. First of all, he's clearly not an otaku, so his mind doesn't automatically jump to that sort of thing like Honami's clearly did. Secondly, he's already admitted how he doesn't fully believe her story of being from another world. As he said, she may not be able to lie because she shows her emotions on her face, but she might not be telling the truth either. Meaning that she REALLY believes that she's from another world even if it might not be true, like some sort of mental condition or delirium or something.