This twin thin is only possible in countries where they use Surnames first, then names when get to know each other better. Cause any other country - the girls would say their names and MC would already know they aren't one person - at least without one of them lying to troll.
Another thing is twins themselves. Had few twins pairs in my school days in even my class. They never pretended to be each-other, they actually tried to make it as obvious as possible to discern them - including, sometimes kinda forcefully, having different tasted in stuff like music, other-sex preferences, etc.
Also this is one more manga I stumbled upon that is basically a carbon copy of a youtube manga dub short video, the other one I remember now is the dude living together with a girl where both of them hated each-other guts, but slowly fall in love with each other - that one had few episodes even on English side.
