Kuroo actually is foreigner but nobody, exept for Kenma, Bokuto and Akaashi, really knows where he is from.
Tetsurou has fun whenever someone tries to guess his homeland, especially when Lev tries to guess because he needs to know for whatever reason.
Kuroo won't tell anyone where he orginally is because he is afraid of prejudices.
Don't judge me, my brain is weird and loves to make the characters come from another country because it loves other countries ¯\_(ツ)_/¯
