@Mnuchinboo
Honestly, i don't know either. I think it's because Takamine was hoping that by being friends with him, he'd be able to let go of his height insecurity. Yuuki kept bringing up his pacing as slow, so to not make Takamine worry(?) he apologises for it and even tells her to leave him...
@Yautja
I think she's begun using Japanese more, but with very few words and very distant occasions. She basically like a foreign kindergartner in terms of speaking Japanese ATM, knows very few words.
But i gotta admit the author needs to release a dictionary of their language or something for...
@AbuHajaar
He met her in the Mountains of South East Asia. Doesn't mean she was born there. Could of been taken in or had also discovered them and decided to live with the people there.
Or she could just be an albino asian.