i get the not using her real name, because her name is korean which probably doesnt exist in that world. their names, so far as on that continent/area, are at the very least...uh well, not korean.
Why use that name? Someone already mistook her for someone else because of her appearance. Now she even uses the same name? That's just asking for trouble... That black haired guy from before is surely not the only person who knows a person called Teishi who looks like her :/